Relevant bibliographies by topics / SEC61 protein

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Academic literature on the topic 'SEC61 protein'

Author: Grafiati
Published: 4 June 2021
Last updated: 7 February 2022

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Journal articles on the topic "SEC61 protein"

1

Witham, Christopher M., Aleshanee L. Paxman, Lamprini Baklous, Robert F. L. Steuart, Benjamin L. Schulz, and Carl J. Mousley. "Cancer associated mutations in Sec61γ alter the permeability of the ER translocase." PLOS Genetics 17, no. 8 (August 30, 2021): e1009780. http://dx.doi.org/10.1371/journal.pgen.1009780.

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Translocation of secretory and integral membrane proteins across or into the ER membrane occurs via the Sec61 complex, a heterotrimeric protein complex possessing two essential sub-units, Sec61p/Sec61α and Sss1p/Sec61γ and the non-essential Sbh1p/Sec61β subunit. In addition to forming a protein conducting channel, the Sec61 complex maintains the ER permeability barrier, preventing flow of molecules and ions. Loss of Sec61 integrity is detrimental and implicated in the progression of disease. The Sss1p/Sec61γ C-terminus is juxtaposed to the key gating module of Sec61p/Sec61α and is important for gating the translocon. Inspection of the cancer genome database identifies six mutations in highly conserved amino acids of Sec61γ/Sss1p. We identify that five out of the six mutations identified affect gating of the ER translocon, albeit with varying strength. Together, we find that mutations in Sec61γ that arise in malignant cells result in altered translocon gating dynamics, this offers the potential for the translocon to represent a target in co-therapy for cancer treatment.
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Sicking, Mark, Martin Jung, and Sven Lang. "Lights, Camera, Interaction: Studying Protein–Protein Interactions of the ER Protein Translocase in Living Cells." International Journal of Molecular Sciences 22, no. 19 (September 26, 2021): 10358. http://dx.doi.org/10.3390/ijms221910358.

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Various landmark studies have revealed structures and functions of the Sec61/SecY complex in all domains of live demonstrating the conserved nature of this ancestral protein translocase. While the bacterial homolog of the Sec61 complex resides in the plasma membrane, the eukaryotic counterpart manages the transfer of precursor proteins into or across the membrane of the endoplasmic reticulum (ER). Sec61 complexes are accompanied by a set of dynamically recruited auxiliary proteins assisting the transport of certain precursor polypeptides. TRAP and Sec62/Sec63 are two auxiliary protein complexes in mammalian cells that have been characterized by structural and biochemical methods. Using these ER membrane protein complexes for our proof-of-concept study, we aimed to detect interactions of membrane proteins in living mammalian cells under physiological conditions. Bimolecular luminescence complementation and competition was used to demonstrate multiple protein–protein interactions of different topological layouts. In addition to the interaction of the soluble catalytic and regulatory subunits of the cytosolic protein kinase A, we detected interactions of ER membrane proteins that either belong to the same multimeric protein complex (intra-complex interactions: Sec61α–Sec61β, TRAPα–TRAPβ) or protein complexes in juxtaposition (inter-complex interactions: Sec61α–TRAPα, Sec61α–Sec63, and Sec61β–Sec63). In the process, we established further control elements like synthetic peptide complementation for expression profiling of fusion constructs and protease-mediated reporter degradation demonstrating the cytosolic localization of a reporter complementation. Ease of use and flexibility of the approach presented here will spur further research regarding the dynamics of protein–protein interactions in response to changing cellular conditions in living cells.
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Witham, Christopher M., Hasindu G. Dassanayake, Aleshanee L. Paxman, Kofi L. P. Stevens, Lamprini Baklous, Paris F. White, Amy L. Black, et al. "The conserved C-terminus of Sss1p is required to maintain the endoplasmic reticulum permeability barrier." Journal of Biological Chemistry 295, no. 7 (December 17, 2019): 2125–34. http://dx.doi.org/10.1074/jbc.ra119.010378.

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The endoplasmic reticulum (ER) is the entry point to the secretory pathway and major site of protein biogenesis. Translocation of secretory and integral membrane proteins across or into the ER membrane occurs via the evolutionarily conserved Sec61 complex, a heterotrimeric channel that comprises the Sec61p/Sec61α, Sss1p/Sec61γ, and Sbh1p/Sec61β subunits. In addition to forming a protein-conducting channel, the Sec61 complex also functions to maintain the ER permeability barrier, preventing the mass free flow of essential ER-enriched molecules and ions. Loss in Sec61 integrity is detrimental and implicated in the progression of disease. The Sss1p/Sec61γ C terminus is juxtaposed to the key gating module of Sec61p/Sec61α, and we hypothesize it is important for gating the ER translocon. The ER stress response was found to be constitutively induced in two temperature-sensitive sss1 mutants (sss1ts) that are still proficient to conduct ER translocation. A screen to identify intergenic mutations that allow for sss1ts cells to grow at 37 °C suggests the ER permeability barrier to be compromised in these mutants. We propose the extreme C terminus of Sss1p/Sec61γ is an essential component of the gating module of the ER translocase and is required to maintain the ER permeability barrier.
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Itskanov, Samuel, and Eunyong Park. "Structure of the posttranslational Sec protein-translocation channel complex from yeast." Science 363, no. 6422 (December 13, 2018): 84–87. http://dx.doi.org/10.1126/science.aav6740.

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The Sec61 protein-conducting channel mediates transport of many proteins, such as secretory proteins, across the endoplasmic reticulum (ER) membrane during or after translation. Posttranslational transport is enabled by two additional membrane proteins associated with the channel, Sec63 and Sec62, but its mechanism is poorly understood. We determined a structure of the Sec complex (Sec61-Sec63-Sec71-Sec72) from Saccharomyces cerevisiae by cryo–electron microscopy (cryo-EM). The structure shows that Sec63 tightly associates with Sec61 through interactions in cytosolic, transmembrane, and ER-luminal domains, prying open Sec61’s lateral gate and translocation pore and thus activating the channel for substrate engagement. Furthermore, Sec63 optimally positions binding sites for cytosolic and luminal chaperones in the complex to enable efficient polypeptide translocation. Our study provides mechanistic insights into eukaryotic posttranslational protein translocation.
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KNIGHT, Bruce C., and Stephen HIGH. "Membrane integration of Sec61α: a core component of the endoplasmic reticulum translocation complex." Biochemical Journal 331, no. 1 (April 1, 1998): 161–67. http://dx.doi.org/10.1042/bj3310161.

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The Sec61 complex is a central component of the endoplasmic reticulum (ER) translocation site. The complex consists of three subunits: Sec61α, Sec61β and Sec61γ, at least two of which (α and β) are adjacent to nascent proteins during membrane insertion. Another component of the translocation machinery is the translocating chain-associating membrane (TRAM) protein, which is also adjacent to many nascent proteins during membrane insertion. Sec61α functions as the major component of a transmembrane channel formed by oligomers of the Sec61 complex. This channel is the site of secretory protein translocation and membrane protein integration at the ER membrane. Sec61α is a polytopic integral membrane protein, and we have studied its biosynthesis and membrane integration in vitro. Using a cross-linking approach to analyse the environment of a series of discrete Sec61α membrane-integration intermediates, we find: (i) newly synthesized Sec61α is adjacent to known components of the ER membrane-insertion site, namely Sec61α, Sec61β and TRAM, and thus the integration of Sec61α appears to require a pre-existing Sec61 complex; (ii) a site-specific cross-linking analysis indicates that the first transmembrane domain of Sec61α remains adjacent to protein components of the ER-insertion site (specifically TRAM and Sec61β) during the insertion of at least three subsequent transmembrane domains; and (iii) the membrane integration of Sec61α requires ER targeting by the signal-recognition particle.
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Stirling, C. J., J. Rothblatt, M. Hosobuchi, R. Deshaies, and R. Schekman. "Protein translocation mutants defective in the insertion of integral membrane proteins into the endoplasmic reticulum." Molecular Biology of the Cell 3, no. 2 (February 1992): 129–42. http://dx.doi.org/10.1091/mbc.3.2.129.

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Yeast mutants defective in the translocation of soluble secretory proteins into the lumen of the endoplasmic reticulum (sec61, sec62, sec63) are not impaired in the assembly and glycosylation of the type II membrane protein dipeptidylaminopeptidase B (DPAPB) or of a chimeric membrane protein consisting of the multiple membrane-spanning domain of yeast hydroxymethylglutaryl CoA reductase (HMG1) fused to yeast histidinol dehydrogenase (HIS4C). This chimera is assembled in wild-type or mutant cells such that the His4c protein is oriented to the ER lumen and thus is not available for conversion of cytosolic histidinol to histidine. Cells harboring the chimera have been used to select new translocation defective sec mutants. Temperature-sensitive lethal mutations defining two complementation groups have been isolated: a new allele of sec61 and a single isolate of a new gene sec65. The new isolates are defective in the assembly of DPAPB, as well as the secretory protein alpha-factor precursor. Thus, the chimeric membrane protein allows the selection of more restrictive sec mutations rather than defining genes that are required only for membrane protein assembly. The SEC61 gene was cloned, sequenced, and used to raise polyclonal antiserum that detected the Sec61 protein. The gene encodes a 53-kDa protein with five to eight potential membrane-spanning domains, and Sec61p antiserum detects an integral protein localized to the endoplasmic reticulum membrane. Sec61p appears to play a crucial role in the insertion of secretory and membrane polypeptides into the endoplasmic reticulum.
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Kalies, Kai-Uwe, Tom A. Rapoport, and Enno Hartmann. "The β Subunit of the Sec61 Complex Facilitates Cotranslational Protein Transport and Interacts with the Signal Peptidase during Translocation." Journal of Cell Biology 141, no. 4 (May 18, 1998): 887–94. http://dx.doi.org/10.1083/jcb.141.4.887.

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The Sec61 complex is the central component of the protein translocation apparatus of the ER membrane. We have addressed the role of the β subunit (Sec61β) during cotranslational protein translocation. With a reconstituted system, we show that a Sec61 complex lacking Sec61β is essentially inactive when elongation and membrane targeting of a nascent chain occur at the same time. The translocation process is perturbed at a step where the nascent chain would be inserted into the translocation channel. However, if sufficient time is given for the interaction of the nascent polypeptide with the mutant Sec61 complex, translocation is almost normal. Thus Sec61β kinetically facilitates cotranslational translocation, but is not essential for it. Using chemical cross-linking we show that Sec61β not only interacts with subunits of the Sec61 complex but also with the 25-kD subunit of the signal peptidase complex (SPC25), thus demonstrating for the first time a tight interaction between the SPC and the Sec61 complex. Interestingly, the cross-links between Sec61β and SPC25 and between Sec61β and Sec61α depend on the presence of membrane-bound ribosomes, suggesting that these interactions are induced when translocation is initiated. We propose that the SPC is transiently recruited to the translocation site, thus enhancing its activity.
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Nelson, M. K., T. Kurihara, and P. A. Silver. "Extragenic suppressors of mutations in the cytoplasmic C terminus of SEC63 define five genes in Saccharomyces cerevisiae." Genetics 134, no. 1 (May 1, 1993): 159–73. http://dx.doi.org/10.1093/genetics/134.1.159.

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Abstract Mutations in the SEC63 gene of Saccharomyces cerevisiae affect both nuclear protein localization and translocation of proteins into the endoplasmic reticulum. We now report the isolation of suppressors of sec63-101 (formerly npl1-1), a temperature-sensitive allele of SEC63. Five complementation groups of extragenic mutations, son1-son5 (suppressor of npl1-1), were identified among the recessive suppressors. The son mutations are specific to SEC63, are not bypass suppressors, and are not new alleles of previously identified secretory (SEC61, SEC62, KAR2) or nuclear protein localization genes (NPL3, NPL4, NPL6). son1 mutations show regional specificity of suppression of sec63 alleles. At low temperatures, son1 mutants grow slowly and show partial mislocalization of nuclear antigens. The SON1 gene maps to chromosome IV and encodes a nuclear protein of 531 amino acids that contains two acidic stretches and a putative nuclear localization sequence. We show that son1 mutations suppress sec63-101 by elimination of Son1p function.
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Baron, Ludivine, Anja Onerva Paatero, Jean-David Morel, Francis Impens, Laure Guenin-Macé, Sarah Saint-Auret, Nicolas Blanchard, et al. "Mycolactone subverts immunity by selectively blocking the Sec61 translocon." Journal of Experimental Medicine 213, no. 13 (November 7, 2016): 2885–96. http://dx.doi.org/10.1084/jem.20160662.

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Mycolactone, an immunosuppressive macrolide released by the human pathogen Mycobacterium ulcerans, was previously shown to impair Sec61-dependent protein translocation, but the underlying molecular mechanism was not identified. In this study, we show that mycolactone directly targets the α subunit of the Sec61 translocon to block the production of secreted and integral membrane proteins with high potency. We identify a single–amino acid mutation conferring resistance to mycolactone, which localizes its interaction site near the lumenal plug of Sec61α. Quantitative proteomics reveals that during T cell activation, mycolactone-mediated Sec61 blockade affects a selective subset of secretory proteins including key signal-transmitting receptors and adhesion molecules. Expression of mutant Sec61α in mycolactone-treated T cells rescued their homing potential and effector functions. Furthermore, when expressed in macrophages, the mycolactone-resistant mutant restored IFN-γ receptor–mediated antimicrobial responses. Thus, our data provide definitive genetic evidence that Sec61 is the host receptor mediating the diverse immunomodulatory effects of mycolactone and identify Sec61 as a novel regulator of immune cell functions.
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Broughton, J., D. Swennen, B. M. Wilkinson, P. Joyet, C. Gaillardin, and C. J. Stirling. "Cloning of SEC61 homologues from Schizosaccharomyces pombe and Yarrowia lipolytica reveals the extent of functional conservation within this core component of the ER translocation machinery." Journal of Cell Science 110, no. 21 (November 1, 1997): 2715–27. http://dx.doi.org/10.1242/jcs.110.21.2715.

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The Sec61 protein is required for protein translocation across the ER membrane in both yeast and mammals and is found in close association with polypeptides during their membrane transit. In Saccharomyces cerevisiae Sec61p is essential for viability and the extent of sequence similarity between the yeast and mammalian proteins (55% sequence identity) suggests that the role of Sec61p in the translocation mechanism is likely to be conserved. In order to further our understanding of the structure and function of Sec61p we have cloned homologues from both Schizosaccharomyces pombe and Yarrowia lipolytica. The S. pombe gene comprises six exons encoding a 479 residue protein which we have immunolocalised to the endoplasmic reticulum. Sequence comparisons reveal that S. pombe Sec61p is 58.6% identical to that of S. cerevisiae. The deduced amino acid sequence of the Y. lipolytica protein shares 68.8% sequence identity with S. cerevisiae Sec61p. Gene disruption studies have shown that the SEC61 is required for viability in both S. pombe and Y. lipolytica demonstrating that the essential nature of this protein is not unique to S. cerevisiae. Moreover, heterologous complementation studies indicate that the Y. lipolytica SEC61 gene can complement a null mutation in S. cerevisiae. Sequence comparisons between the various eukaryotic Sec61p homologues reveal a number of highly conserved domains, including several transmembrane sequences and the majority of cytosolic loops. These comparisons will provide an important framework for the detailed analysis of interactions between Sec61p and other components of the translocation machinery and between Sec61p and translocating polypeptide chains.
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Dissertations / Theses on the topic "SEC61 protein"

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Meyer, Hellmuth-Alexander. "Identifizierung und Charakterisierung evolutionär konservierter Komponenten des Protein-Translokationsapparates im Endoplasmatischen Retikulum." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2001. http://dx.doi.org/10.18452/14625.

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Im Gegensatz zur den monomeren Leaderpeptidasen der bakteriellen Plasmamembran bestehen die eukaryotischen Signalpeptidasen der ER-Membran aus einem heteromeren Protein-Komplex. In der Hefe S. cerevisiae setzt sich die Signalpeptidase aus den vier Membranproteinen Sec11p, Spc1p, Spc2p und Spc3p zusammen. Neben der zur prokaryontischen Leaderpeptidase homologen Untereinheit Sec11p wird auch Spc3p benötigt um die Spaltungsfunktion in der Zelle auszuüben. Die Deletion von SPC3 führt zu einer lethalen Akkumulation von sekretorischen Vorstufenproteinen in vivo, sowie zum Verlust der Spaltungsaktivität in vitro. Spc1p und Spc2p sind nicht essentiell für die Hefe. Für Spc2p konnte jedoch gezeigt werden, daß die Signalpeptidase über die Spc2p Untereinheit mit den b-Untereinheiten des Sec61-Komplexes und des Ssh1-Komplexes interagiert. Vermutlich wird es so dem Komplex ermöglicht, während des Translokationsprozesses engen Kontakt zu der im Translokationskanal befindlichen Signalsequenz aufzunehmen. Im zweiten Teil der Arbeit wurden neue Komponenten aus der ER Membran von Säugern aufgereinigt. Dabei wurde ein ribosomenfreier Sec61-Komplex entdeckt, der mit zwei weiteren Membranproteinen assoziiert ist. Die beiden neuen Membranproteine weisen Homologien zu essentiellen Untereinheiten des postranslational aktiven Sec-Komplexes der Hefe S. cerevisiae auf. Die Rolle des neu entdeckten Säugerkomplexes während der Proteintranslokation ist noch unbekannt, in der Arbeit werden mögliche Funktionen des Komplexes diskutiert.
In contrast to the monomer leaderpeptidase of the prokaryotic plasmamembrane, the eukaryotic signalpeptidase of the ER-membrane is a heteromer protein complex. In yeast the signalpeptidase consist of the four subunits Sec11p, Spc1p, Spc2p and Spc3p. Additional to Sec11p also Spc3p is essential for cell growth and cell life. The depletion of Spc3p cause lethal accumulation of precursor proteins in vivo and lost of cleavage activity in vitro. Spc1p and Spc2p are not essential for the cell. We show here, that the Spc2p subunit interacts with the ß-subunits of the Sec61- and the Ssh1-complex. These data implicate that Spc2p facilitates the interactions between different components of the translocation site. In yeast, efficient protein transport across the endoplasmic reticulum (ER) membrane may occurco-translationally or post-translationally. The latter process is mediated by a membrane protein complex that consists of the Sec61p complex and the Sec62p-Sec63p subcomplex. In contrast, in mammalian cells protein translocation is almost exclusively co-translational. This transport depends on the Sec61 complex, which is homologous to the yeast Sec61p complex and has been identified in mammals as a ribosome-bound pore-forming membrane protein complex. We report here the existence of ribosome-free mammalian Sec61 complexes that associate with two ubiquitous proteins of the ER membrane. According to primary sequence analysis both proteins display homology to the yeast proteins Sec62p and Sec63p and are therefore named Sec62 and Sec63, respectively. The probable function of the mammalian Sec61-Sec62-Sec63 complex is discussed with respect to its abundance in ER membranes, which, in contrast to yeast ER membranes, apparently lack efficient post-translational translocation activity.
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Finke, Kerstin. "Untersuchung paraloger SEC61-Gene und -Proteine in Eukaryoten." Doctoral thesis, [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=958209375.

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Park, Eunyong. "Mechanistic Studies of SecY-Mediated Protein Translocation in Intact Escherichia coli Cells." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10172.

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During the synthesis of secretory and membrane proteins, polypeptides move through a universally conserved protein-conducting channel, formed by the Sec61/SecY complex that is located in the eukaryotic endoplasmic reticulum membrane or the prokaryotic plasma membrane. The channel operates in two different modes depending on its binding partners. In co-translational translocation, a pathway found in all organisms, the channel associates with a translating ribosome. In post-translational translocation, the channel cooperates with either the Sec62–Sec63 complex in eukaryotes or the SecA ATPase in bacteria. Despite tremendous progress in our understanding of protein translocation over the past decades, many questions about its mechanism remain to be answered. These include (1) how the channel maintains the membrane barrier for small molecules while transporting large proteins, (2) what is the functional implication of channel oligomerization, and (3) how the channel interacts with binding partners and polypeptide substrates during translocation. To address these questions, we developed a novel in vivo method to generate both co- and post-translation translocation intermediates in intact Escherichia coli cells, such that polypeptide chains are only partially translocated through the channel. Using this method, we first demonstrated that a translocating polypeptide itself blocks small molecules from passing through an open SecY channel. A hydrophobic pore ring surrounding the polypeptide chain is vital for maintaining the membrane barrier during translocation. Next, we examined the importance of SecY oligomerization in protein translocation. Crosslinking experiments showed that SecY molecules interact with each other in native membranes, but that this self-association is greatly decreased upon insertion of polypeptide substrates. We also showed that SecY mutants that cannot form oligomers are still functional in vivo. Collectively, our data indicate that a single copy of SecY is sufficient for protein translocation. Finally, we isolated an intact co-translational translocation intermediate from E. coli cells and analyzed its structure by cryo-electron microscopy. An initial map shows a translating ribosome containing all three tRNAs is bound to one copy of the SecY channel. Analysis of a large dataset is ongoing in order to understand the structural basis of how the channel interacts with the ribosome and translocating nascent chain.
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Kelkar, Anshuman. "Fucntional analysis of Sec61beta, a component of the Sec61 protein translocation channel at the endoplasmic reticulum." [S.l. : s.n.], 2005. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11811219.

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Raden, David. "Interaction Between Ribosome-Nascent Chain and sec61 Complexes and Their Role in the Translocation of Proteins Across the Endoplasmic Reticulum Membrane: a Thesis." eScholarship@UMMS, 2000. http://escholarship.umassmed.edu/gsbs_diss/257.

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Proteins with RER-specific signal sequences are cotranslationally translocated across the rough endoplasmic reticulum through a proteinaceous channel composed of oligomers of the Sec61 complex. The Sec61 complex also binds ribosomes with high affinity. The dual function of the Sec61 complex necessitates a mechanism to prevent signal sequence-independent binding of ribosomes to the translocation channel. We have examined the hypothesis that the signal recognition particle (SRP) and the nascent polypeptide-associated complex (NAC) respectively act as positive and negative regulatory factors to mediate the signal sequence-specific attachment of the ribosome-nascent chain complex (RNC) to the translocation channel. Here, SRP-independent translocation of a nascent secretory polypeptide was shown to occur in the presence of endogenous wheat germ or rabbit reticulocyte NAC. Furthermore, SRP markedly enhanced RNC binding to the translocation channel irrespective of the presence of NAC. Binding of RNCs, but not SRP-RNCs, to the Sec61 complex is competitively inhibited by 80S ribosomes. Thus, the SRP dependent targeting pathway provides a mechanism for delivery of RNCs to the translocation channel that is not inhibited by the non-selective interaction between the ribosome and the Sec61 complex. The Sec61 complex, serving as both the high affinity ribosome receptor and the translocation channel, is performing two very different functions which presumably requires different activity domains within the Sec61 complex. To define regions of the Sec61 complex that are involved in ribosome binding and translocation promotion, ribosome-stripped microsomes were subjected to limited digestions using proteases with different cleavage specificities. Protein immunoblot analysis using antibodies specific for the N and C-terminus of Sec61α was used to map the location of proteolysis cleavage sites. We observed a striking correlation between a loss of ribosome binding activity and the digestion of the C-terminal tail or cytoplasmic loop 8 of Sec61α. The proteolyzed microsomes were assayed for SRP-independent translocation activity to determine whether ribosome binding to the Sec61 complex is a prerequisite for nascent chain transport. Microsomes that do not bind ribosomes with high affinity at physiological ionic strength remain active in SRP-independent translocation indicating that ribosome binding and translocation promotion are separable activities of the Sec61 complex. Translocation promoting activity was most severely inhibited by cleavage of cytosolic loop 6, indicating that this segment is a critical determinant for this function of the Sec61 complex.
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Boekel, Carolina. "Integration and topology of membrane proteins." Doctoral thesis, Stockholm : Department of Biochemistry and Biophysics, Stockholm University, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-8575.

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Cheng, Zhiliang. "Posttargeting Events in Cotranslational Translocation Through the Sec61 Complex: a Thesis." eScholarship@UMMS, 2006. https://escholarship.umassmed.edu/gsbs_diss/1.

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The cytoplasmic surface of Sec61p is the binding site for the ribosome and has been proposed to interact with the signal recognition particle receptor during targeting of the ribosome nascent chain complex to the translocation channel. Point mutations in cytoplasmic loops six (L6) and eight (L8) of yeast Sec61p cause reductions in growth rates and defects in translocation of nascent polypeptides that utilize the cotranslational translocation pathway. Sec61 heterotrimers isolated from the L8 sec61 mutants have a greatly reduced affinity for 80S ribosomes. Cytoplasmic accumulation of protein precursors demonstrates that the initial contact between the large ribosomal subunit and the Sec61 complex is important for efficient insertion of a nascent polypeptide into the translocation pore. In contrast, point mutations in L6 of Sec61p inhibit cotranslational translocation without significantly reducing the ribosome binding activity, indicating that the L6 and L8 sec61 mutants impact different steps in the cotranslational translocation pathway. Integral membrane proteins are cotranslationally inserted into the endoplasmic reticulum via the protein translocation channel, which mediates the translocation of lumenal domains, retention of cytosolic domains and integration of transmembrane spans into the phospholipid bilayer. We analyzed the in vivo kinetics of integration of model membrane proteins in Saccharomyces cerevisiae using ubiquitin translocation assay reporters. A signal anchor sequence from a type II membrane protein gates the translocon pore less rapidly than a cleavable signal sequence from a secretory protein. Transmembrane spans and lumenal domains are exposed to the cytosol during integration of a poly topic membrane protein. The conformational changes in the translocon that permit opening of the lumenal and lateral channel gates occur less rapidly than elongation of the nascent polypeptide. Cytosolic exposure of transmembrane spans and lumenal domains poses a challenge to the fidelity of membrane protein integration.
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Falke, Kristian. "Ein 3D-Modell des Ribosomen-gebundenen OST-Sec61-Translokons." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2012. http://dx.doi.org/10.18452/16595.

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Gleich einem Etikett dient die N-Glykokosylierung vom Ribosom neu synthetisierter Proteine durch die Oligosaccharyltransferase (OST) bei der kotranslationalen Translokation in das Endoplasmatische Retikulum (ER) als Startpunkt vielschichtiger Prozessierungen. Bisher fehlte der strukturelle Nachweis, dass die OST als mit dem Ribosom assoziierten Membranprotein (RAMP) Bestandteil des auf dem proteinleitenden Kanal, dem Sec61-Komplex, basierenden Translokons ist. In dieser Arbeit berichten wir von der kryoelektronenmikroskopischen 3D-Struktur eines definierten OST-Sec61-Ribosom-Komplexes aus Saccharomyces cerevisiae bei 15,4 Å Auflösung. Dazu wurden die Komponenten (OST, Sec61 und Ribosomen mit naszierender Proteinkette) affinitätschromatographisch gereinigt und das Bindungsverhalten mit 80S-Ribosomen in vitro untersucht. Die OST band mit einer KD von 12,8 nM hochaffin und spezifisch an den bekannten Sec61-Ribosomen-Komplex. Dieser in vitro rekonstituierte trimere Komplex zeigte eine neuartige eng an das Ribosom anschließende Translokonstruktur mit zwei bisher unbekannten ribosomalen Verbindungen, einer einzigen dezentralen porenförmigen Vertiefung und zusätzlichen luminalen Bereichen. Durch das Docken eines Sec61-Homologs in einer alternativen Bindeposition sowie das Docken eines Stt3p-Homologs (der katalytischen Untereinheit der OST) und mit Hilfe der mittels (Kryo-)Negativkontrastierung gewonnenen 3D-Struktur der OST konnten Hybridmodelle erstellt werden. Daraus wurde unter Einbeziehung von bekannten molekularbiologisch gewonnenen Interaktionsdaten das 3D-Modell eines aktiven Ribosomen-gebundenen OST-Sec61-Translokons entwickelt.
Like a label, N-glycosylation by the oligosaccharyltransferase (OST) of newly synthesized proteins emerging from the ribosome while being cotranslationally translocated into the endoplasmic reticulum (ER) provides a starting point for a multitude of processes. Hitherto no structural proof has been presented, that the OST as a ribosome associated membrane protein (RAMP) is a constituent of the translocon, based at its core on the protein conducting channel (Sec61-complex). In this work we report on the 3D-structure of a defined OST-Sec61-ribosome complex from Saccharomyces cerevisiae by cryo-electron microscopy at 15.4 Å resolution. Thereto, the components (OST, Sec61, ribosome nascent chain complexes) have been purified by affinity chromatography and the binding of 80S-ribosomes has been checked in vitro. The OST bound with high affinity by a KD of 12.8 nM specifically to the established Sec61-ribosome complex. This trimeric complex reconstituted in vitro exhibits a new kind of tightly bound ribosomal translocon showing two hitherto unknown connections to the ribosome, a single off-center pore-like indentation and an additional luminal domain. By docking of a Sec61 homologue at an alternative binding position plus the docking of a Stt3p homologue (the catalytic subunit of the OST) and by means of the 3D-structure of the OST using the (cryo-)negative staining technique, hybrid models could be created. Consequently, integrating known interaction data from molecular biology experiments has been used to develop a 3D-model of an active ribosome-bound OST-Sec61-translocon.
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9

Brewer, Daniel Niron. "Elucidation of the Role of the Exocyst Subunit Sec6p in Exocytosis: A Dissertation." eScholarship@UMMS, 2009. https://escholarship.umassmed.edu/gsbs_diss/446.

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Abstract:
Trafficking of protein and lipid cargo through the secretory pathway in eukaryotic cells is mediated by membrane-bound vesicles. Secretory vesicles are targeted to sites of exocytosis on the plasma membrane in part by a conserved multi-subunit protein complex termed the exocyst. In addition to tethering vesicles to the plasma membrane, the exocyst complex and components therein may also add a layer of regulation by directly controlling assembly of the SNARE complex, which is required for membrane fusion, as well as other regulatory factors such as Sec1p. In the past, we have shown that Sec6p interacts with Sec9p in vivo and that that interaction retards binary SNARE complex formation in a SNARE assembly assay. Though many interactions have been mapped using in vitro methods, confirming them in vivoand placing them into the context of a complete model that accounts for all observed interactions (and lack of interactions) has proven difficult. In order to address these problems, I have studied the interactions between Sec6p and other factors involved in exocytosis at the plasma membrane via in vivo methods. My hypothesis was that Sec6p interaction with Sec9p and subsequent inhibition of SNARE complex assembly in vitro was an intermediate state and Sec6p was part of a set of cofactors that accelerated SNARE complex assembly in vivo. To test this hypothesis I showed that the interaction between the plasma membrane t-SNARE Sec9p and the yeast exocyst subunit Sec6p can be observed in vivoand designed point mutations to disrupt that interaction. Interestingly, I also showed that Sec6p:Sec9p interaction involves the free pool of Sec6p rather than the exocyst bound fraction of Sec6p. Point mutations in the N-terminal domain of Sec6p result in temperature sensitive growth and secretion defects, without loss of Sec6p-Sec9p interaction. However, at the non-permissive temperature, the exocyst subunits Sec5p, Sec10p and Sec15p are mislocalized and are absent from the exocyst complex. The resulting subcomplex, containing Sec3p, Sec8p, Exo70p and Exo84p, remains stably assembled and localized at sites of polarized secretion. This subcomplex is likely due to disruption of interaction between Sec6p and Sec5p, and may be similar to that observed at restrictive temperatures in the sec6-54temperature sensitive mutant. Additionally, one of the sec6 temperature sensitive mutants displays a loss of binding to the yeast regulatory protein Sec1p. In vitro binding studies indicate a direct interaction between Sec1p and the free pool of the wild-type Sec6p protein, suggesting close interplay between Sec6p and Sec1p in the regulation of SNARE complexes. A coherent model which incorporates all these interactions has continued to be elusive. However, the results I have found do suggest several hypotheses which should prove testable in the future.
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10

Dubuke, Michelle L. "The Exocyst Subunit Sec6 Interacts with Assembled Exocytic Snare Complexes: A Dissertation." eScholarship@UMMS, 2015. https://escholarship.umassmed.edu/gsbs_diss/868.

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In eukaryotic cells, membrane-bound vesicles carry cargo between intracellular compartments, to and from the cell surface, and to the extracellular environment. Many conserved families of proteins are required for properly localized vesicle fusion, including the multi-subunit tethering complexes and the SNARE complexes. These protein complexes work together to promote proper vesicle fusion in other trafficking pathways. Contrary to these other pathways, our lab previously suggested that the exocyst subunit Sec6, a component of the exocytosis-specific tethering complex, inhibited Sec9:Sso1 SNARE complex assembly due to interactions in vitro with the SNARE protein Sec9 (Sivaram et al., 2005). My goal for this project was to test the hypothesis that Sec6 inhibited SNARE complex assembly in vivo. I therefore chose to generate Sec6:Sec9 loss-of-binding mutants, and study their effect both in vitro and in vivo. I identified a patch of residues on Sec9 that, when mutated, are sufficient to disrupt the novel Sec6-SNARE interaction. Additionally, I found that the previous inhibitory role for Sec6 in SNARE assembly was due to a data mis-interpretation; my re-interpretation of the data shows that Sec6 has a mild, if any, inhibitory effect on SNARE assembly. My results suggest a potential positive role for Sec6 in SNARE complex assembly, similar to the role observed for other tether-SNARE interactions.
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Books on the topic "SEC61 protein"

1

Norbury, Louise Clare. The biosynthesis of Sec61[alpha]: A membrane protein of the endoplasmic retriculum. Manchester: University of Manchester, 1996.

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2

Hewitt, Eric Wilfrid. Investigation into the role of the SEC65 gene product in protein translocation across the yeast ER membrane. Manchester: University of Manchester, 1994.

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Book chapters on the topic "SEC61 protein"

1

Stirling, Colin J. "Similarities between S. cerevisiae SEc61p and E. coli SecY Suggest a Common Origin for Protein Translocases of the Eukaryotic ER and the Bacterial Plasma Membrane." In Protein Synthesis and Targeting in Yeast, 293–305. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-84921-3_27.

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Yu, Haijia, Lauren Crisman, Michael H. B. Stowell, and Jingshi Shen. "Functional Reconstitution of Intracellular Vesicle Fusion Using Purified SNAREs and Sec1/Munc18 (SM) Proteins." In Methods in Molecular Biology, 237–49. New York, NY: Springer New York, 2018. http://dx.doi.org/10.1007/978-1-4939-8760-3_15.

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"Structure of the Sec61-Complex." In Protein Transport into the Endoplasmic Reticulum, 67–74. CRC Press, 2009. http://dx.doi.org/10.1201/9781498714013-9.

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Grewal, Iqbal. "Overview Of Antibody- Based Therapeutics Present And Future Promise." In Emerging Protein Biotherapeutics. CRC Press, 2009. http://dx.doi.org/10.1201/9781420063219.sec1.

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Dziuba, Jerzy, and Anna Iwaniak. "Database of Protein and Bioactive Peptide Sequences." In Nutraceutical Proteins and Peptides in Health and Disease, 543–63. CRC Press, 2005. http://dx.doi.org/10.1201/9781420028836.sec6.

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Mine, Yoshinori, and Fereidoon Shahidi. "Nutraceutical Proteins and Peptides in Health and Disease." In Nutraceutical Proteins and Peptides in Health and Disease, 3–9. CRC Press, 2005. http://dx.doi.org/10.1201/9781420028836.sec1.

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Dehouck, Y., D. Gilis, and M. Rooman. "In Silico to in Vitro Approach for Protein Folding and Misfolding." In Amyloid and Amyloidosis, 3–5. CRC Press, 2004. http://dx.doi.org/10.1201/9781420037494.sec1.

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Weimer, Robby M., and Janet E. Richmond. "Synaptic Vesicle Docking: A Putative Role for the Munc18⧸Sec1 Protein Family." In Current Topics in Developmental Biology, 83–113. Elsevier, 2004. http://dx.doi.org/10.1016/s0070-2153(04)65003-4.

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Coury, Larry A., Mark L. Zeidel, and Jeffrey L. Brodsky. "[10] Use of yeast sec6 mutant for purification of vesicles containing recombinant membrane proteins." In Methods in Enzymology, 169–86. Elsevier, 1999. http://dx.doi.org/10.1016/s0076-6879(99)06012-7.

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Conference papers on the topic "SEC61 protein"

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Lowe, Eric, Janet L. Anderl, Andrea R. Fan, Jing Jiang, Henry W. Johnson, Christopher J. Kirk, Dustin McMinn, Tony Muchamuel, Jack Taunton, and Jennifer A. Whang. "Abstract 3087: KZR-8834: A novel, small molecule inhibitor of Sec61-dependent protein secretion with anti-tumor activity." In Proceedings: AACR Annual Meeting 2019; March 29-April 3, 2019; Atlanta, GA. American Association for Cancer Research, 2019. http://dx.doi.org/10.1158/1538-7445.am2019-3087.

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Lowe, Eric, Janet L. Anderl, Andrea R. Fan, Jing Jiang, Henry W. Johnson, Christopher J. Kirk, Dustin McMinn, Tony Muchamuel, Jack Taunton, and Jennifer A. Whang. "Abstract 3087: KZR-8834: A novel, small molecule inhibitor of Sec61-dependent protein secretion with anti-tumor activity." In Proceedings: AACR Annual Meeting 2019; March 29-April 3, 2019; Atlanta, GA. American Association for Cancer Research, 2019. http://dx.doi.org/10.1158/1538-7445.sabcs18-3087.

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Kasoha, M., Z. Takacs, RM Bohle, G. Schmidt, M. Linxweiler, B. Schick, I. Juhasz-Böss, and EF Solomayer. "Protein expression of SEC62 in triple-negative breast cancer." In 62. Kongress der Deutschen Gesellschaft für Gynäkologie und Geburtshilfe – DGGG'18. Georg Thieme Verlag KG, 2018. http://dx.doi.org/10.1055/s-0038-1671046.

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Kasoha, M., Z. Takacs, J. Radosa, R. Bohle, G. Schmidt, M. Linxweiler, B. Schick, I. Juhasz-Böss, and EF Solomayer. "Protein expression of SEC62 in triple-negative breast cancer." In Abstracts of the 10th Scientific Symposium of the Comission for Translational Research of the Working group for Gynecologic Oncology AGO e.V. Georg Thieme Verlag KG, 2018. http://dx.doi.org/10.1055/s-0038-1675454.

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