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Artykuły w czasopismach na temat "Sigme proteins"
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Raman, Sahadevan, Xiaoling Puyang, Tan-Yun Cheng, David C. Young, D. Branch Moody, and Robert N. Husson. "Mycobacterium tuberculosis SigM Positively Regulates Esx Secreted Protein and Nonribosomal Peptide Synthetase Genes and Down Regulates Virulence-Associated Surface Lipid Synthesis." Journal of Bacteriology 188, no. 24 (2006): 8460–68. http://dx.doi.org/10.1128/jb.01212-06.
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ABSTRACT The Mycobacterium tuberculosis genome encodes 12 alternative sigma factors, several of which regulate stress responses and are required for virulence in animal models of acute infection. In this work we investigated M. tuberculosis SigM, a member of the extracytoplasmic function subfamily of alternative sigma factors. This sigma factor is expressed at low levels in vitro and does not appear to function in stress response regulation. Instead, SigM positively regulates genes required for the synthesis of surface or secreted molecules. Among these are genes encoding two pairs of Esx secreted proteins, a multisubunit nonribosomal peptide synthetase operon, and genes encoding two members of the proline-proline-glutamate (PPE) family of proteins. Genes up regulated in a sigM mutant strain include a different PPE gene, as well as several genes involved in surface lipid synthesis. Among these are genes involved in synthesis of phthiocerol dimycocerosate (PDIM), a surface lipid critical for virulence during acute infection, and the kasA-kasB operon, which is required for mycolic acid synthesis. Analysis of surface lipids showed that PDIM synthesis is increased in a sigM-disrupted strain and is undetectable in a sigM overexpression strain. These findings demonstrate that SigM positively and negatively regulates cell surface and secreted molecules that are likely to function in host-pathogen interactions.
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Nakunst, Diana, Christof Larisch, Andrea T. Hüser, Andreas Tauch, Alfred Pühler, and Jörn Kalinowski. "The Extracytoplasmic Function-Type Sigma Factor SigM of Corynebacterium glutamicum ATCC 13032 Is Involved in Transcription of Disulfide Stress-Related Genes." Journal of Bacteriology 189, no. 13 (2007): 4696–707. http://dx.doi.org/10.1128/jb.00382-07.
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ABSTRACT The gene for the extracytoplasmic function (ECF) sigma factor SigM was deleted from the chromosome of the gram-positive soil bacterium Corynebacterium glutamicum to elucidate the role of the SigM protein in the regulation of gene expression. Comparative DNA microarray hybridizations of the C. glutamicum wild type and sigM-deficient mutant C. glutamicum DN1 revealed 23 genes with enhanced expression in the sigM-proficient strain, encoding functions in the assembly of iron-sulfur clusters (suf operon), thioredoxin reductase (trxB), thioredoxins (trxC, trxB1), chaperones (groES, groEL, clpB), and proteins involved in the heat shock response (hspR, dnaJ, grpE). Deletion of the sigM gene rendered the C. glutamicum cells more sensitive to heat, cold, and the presence of the thiol oxidant diamide. Transcription of the sigM gene increased under different stress conditions, including heat shock, cold shock, and disulfide stress caused by diamide treatment, suggesting a regulatory role for SigM under thiol-oxidative stress conditions. Stress-responsive promoters were determined upstream of the suf operon and of the trxB, trxC, and trxB1 genes. The deduced SigM consensus promoter is characterized by the −35 hexamer gGGAAT and the −10 hexamer YGTTGR. Transcription of the sigM gene is apparently controlled by the ECF sigma factor SigH, since a sigH mutant was unable to enhance the expression of sigM and the SigM regulon under thiol-oxidative stress conditions. A typical SigH-responsive promoter was mapped upstream of the sigM gene. The ECF sigma factor SigM is apparently part of a regulatory cascade, and its transcription is controlled by SigH under conditions of thiol-oxidative stress.
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Fernandes, Norvin D., Qi-long Wu, Dequan Kong, Xiaoling Puyang, Sumeet Garg, and Robert N. Husson. "A Mycobacterial Extracytoplasmic Sigma Factor Involved in Survival following Heat Shock and Oxidative Stress." Journal of Bacteriology 181, no. 14 (1999): 4266–74. http://dx.doi.org/10.1128/jb.181.14.4266-4274.1999.
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ABSTRACT Extracytoplasmic function (ECF) sigma factors are a heterogeneous group of alternative sigma factors that regulate gene expression in response to a variety of conditions, including stress. We previously characterized a mycobacterial ECF sigma factor, SigE, that contributes to survival following several distinct stresses. A gene encoding a closely related sigma factor, sigH, was cloned fromMycobacterium tuberculosis and Mycobacterium smegmatis. A single copy of this gene is present in these and other fast- and slow-growing mycobacteria, including M. fortuitum and M. avium. While the M. tuberculosis and M. smegmatis sigH genes encode highly similar proteins, there are multiple differences in adjacent genes. The single in vivo transcriptional start site identified inM. smegmatis and one of two identified in M. bovis BCG were found to have −35 promoter sequences that match the ECF-dependent −35 promoter consensus. Expression from these promoters was strongly induced by 50°C heat shock. In comparison to the wild type, an M. smegmatis sigH mutant was found to be more susceptible to cumene hydroperoxide stress but to be similar in logarithmic growth, stationary-phase survival, and survival following several other stresses. Survival of an M. smegmatis sigH sigE double mutant was found to be markedly decreased following 53°C heat shock and following exposure to cumene hydroperoxide. Expression of the second gene in the sigH operon is required for complementation of the sigH stress phenotypes. SigH is an alternative sigma factor that plays a role in the mycobacterial stress response.
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Singh, Rakesh Kumar, Lav Kumar Jaiswal, Tanmayee Nayak, et al. "Expression, Purification, and In Silico Characterization of Mycobacterium smegmatis Alternative Sigma Factor SigB." Disease Markers 2022 (May 20, 2022): 1–11. http://dx.doi.org/10.1155/2022/7475704.
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Sigma factor B (SigB), an alternative sigma factor (ASF), is very similar to primary sigma factor SigA (σ70) but dispensable for growth in both Mycobacterium smegmatis (Msmeg) and Mycobacterium tuberculosis (Mtb). It is involved in general stress responses including heat, oxidative, surface, starvation stress, and macrophage infections. Despite having an extremely short half-life, SigB tends to operate downstream of at least three stress-responsive extra cytoplasmic function (ECF) sigma factors (SigH, SigE, SigL) and SigF involved in multiple signaling pathways. There is very little information available regarding the regulation of SigB sigma factor and its interacting protein partners. Hence, we cloned the SigB gene into pET28a vector and optimized its expression in three different strains of E. coli, viz., (BL21 (DE3), C41 (DE3), and CodonPlus (DE3)). We also optimized several other parameters for the expression of recombinant SigB including IPTG concentration, temperature, and time duration. We achieved the maximum expression of SigB at 25°C in the soluble fraction of the cell which was purified by affinity chromatography using Ni-NTA and further confirmed by Western blotting. Further, structural characterization demonstrates the instability of SigB in comparison to SigA that is carried out using homology modeling and structure function relationship. We have done protein-protein docking of RNA polymerase (RNAP) of Msmeg and SigB. This effort provides a platform for pulldown assay, structural, and other studies with the recombinant protein to deduce the SigB interacting proteins, which might pave the way to study its signaling networks along with its regulation.
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White, Mark J., Hongjun He, Renee M. Penoske, Sally S. Twining, and Thomas C. Zahrt. "PepD Participates in the Mycobacterial Stress Response Mediated through MprAB and SigE." Journal of Bacteriology 192, no. 6 (2010): 1498–510. http://dx.doi.org/10.1128/jb.01167-09.
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ABSTRACT Currently, one-third of the world's population is believed to be latently infected with Mycobacterium tuberculosis. The mechanisms by which M. tuberculosis establishes latent infection remain largely undefined. mprAB encodes a two-component signal transduction system required by M. tuberculosis for aspects of persistent infection. MprAB regulates a large and diverse group of genetic determinants in response to membrane stress, including the extracytoplasmic function (ECF) sigma factor sigE and the HtrA-like serine protease pepD. Recent studies have demonstrated that PepD functions as both a protease and chaperone in vitro. In addition, inactivation of pepD alters the virulence of M. tuberculosis in a mouse model system of infection. Here, we demonstrate that PepD plays an important role in the stress response network of Mycobacterium mediated through MprAB and SigE. In particular, we demonstrate that the protease activity of PepD requires the PDZ domain, in addition to the catalytic serine at position 317. pepD expression initiates from at least three promoters in M. tuberculosis, including one that is regulated by SigE and is located upstream of the mprA coding sequence. Deletion of pepD or mprAB in Mycobacterium smegmatis and M. tuberculosis alters the stress response phenotypes of these strains, including increasing sensitivity to SDS and cell wall antibiotics and upregulating the expression of stress-responsive determinants, including sigE. Taking these data together, we hypothesize that PepD utilizes its PDZ domain to recognize and process misfolded proteins at the cell membrane, leading to activation of the MprAB and SigE signaling pathways and subsequent establishment of a positive feedback loop that facilitates bacterial adaptation.
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Kim, Eun Sook, Ju Yeon Song, Dae Wi Kim, Keith F. Chater, and Kye Joon Lee. "A Possible Extended Family of Regulators of Sigma Factor Activity in Streptomyces coelicolor." Journal of Bacteriology 190, no. 22 (2008): 7559–66. http://dx.doi.org/10.1128/jb.00470-08.
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ABSTRACT SCO4677 is one of a large number of similar genes in Streptomyces coelicolor that encode proteins with an HATPase_c domain resembling that of anti-sigma factors such as SpoIIAB of Bacillus subtilis. However, SCO4677 is not located close to genes likely to encode a cognate sigma or anti-anti-sigma factor. SCO4677 was found to regulate antibiotic production and morphological differentiation, both of which were significantly enhanced by the deletion of SCO4677. Through protein-protein interaction screening of candidate sigma factor partners using the yeast two-hybrid system, SCO4677 protein was found to interact with the developmentally specific σF, suggesting that it is an antagonistic regulator of σF. Two other proteins, encoded by SCO0781 and SCO0869, were found to interact with the SCO4677 anti-σF during a subsequent global yeast two-hybrid screen, and the SCO0869-SCO4677 protein-protein interaction was confirmed by coimmunoprecipitation. The SCO0781 and SCO0869 proteins resemble well-known anti-anti-sigma factors such as SpoIIAA of B. subtilis. It appears that streptomycetes may possess an extraordinary abundance of anti-sigma factors, some of which may influence diverse processes through interactions with multiple partners: a novel feature for such regulatory proteins.
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Kazmierczak, Mark J., Martin Wiedmann, and Kathryn J. Boor. "Alternative Sigma Factors and Their Roles in Bacterial Virulence." Microbiology and Molecular Biology Reviews 69, no. 4 (2005): 527–43. http://dx.doi.org/10.1128/mmbr.69.4.527-543.2005.
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SUMMARY Sigma factors provide promoter recognition specificity to RNA polymerase holoenzyme, contribute to DNA strand separation, and then dissociate from the core enzyme following transcription initiation. As the regulon of a single sigma factor can be composed of hundreds of genes, sigma factors can provide effective mechanisms for simultaneously regulating expression of large numbers of prokaryotic genes. One newly emerging field is identification of the specific roles of alternative sigma factors in regulating expression of virulence genes and virulence-associated genes in bacterial pathogens. Virulence genes encode proteins whose functions are essential for the bacterium to effectively establish an infection in a host organism. In contrast, virulence-associated genes can contribute to bacterial survival in the environment and therefore may enhance the capacity of the bacterium to spread to new individuals or to survive passage through a host organism. As alternative sigma factors have been shown to regulate expression of both virulence and virulence-associated genes, these proteins can contribute both directly and indirectly to bacterial virulence. Sigma factors are classified into two structurally unrelated families, the σ70 and the σ54 families. The σ70 family includes primary sigma factors (e.g., Bacillus subtilis σA) as well as related alternative sigma factors; σ54 forms a distinct subfamily of sigma factors referred to as σN in almost all species for which these proteins have been characterized to date. We present several examples of alternative sigma factors that have been shown to contribute to virulence in at least one organism. For each sigma factor, when applicable, examples are drawn from multiple species.
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S Thompson, L., and E. J Harry. "Alternative sigma factors: the master regulators." Microbiology Australia 27, no. 3 (2006): 118. http://dx.doi.org/10.1071/ma06118.
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When a bacterial cell encounters a change in environmental conditions, it responds by producing a different complement of cellular proteins. Which proteins are produced and maintained is regulated in a number of ways, including regulation of gene transcription, stabilising or degrading mRNA transcripts, post translational modifications and targeted degradation of proteins.
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Yang, Fumeng, Wenjun Wang, Qian Liu, et al. "The application of Six Sigma to perform quality analyses of plasma proteins." Annals of Clinical Biochemistry: International Journal of Laboratory Medicine 57, no. 2 (2019): 121–27. http://dx.doi.org/10.1177/0004563219892023.
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Background The Six Sigma theory is an important tool for laboratory quality management. It has been widely used in clinical chemistry, haematology and other disciplines. The aim of our study was to evaluate the analytical performance of plasma proteins by application of Sigma metric and to compare the differences among three different allowable total errors in evaluating the analytical performance of plasma proteins. Methods Three different allowable total error values were used as quality goals. Data from an external quality assessment were used as bias, and the cumulative coefficient of variation in internal quality control data was used to represent the amount of imprecision during the same period. Sigma metric of analytes was calculated using the above data. The quality goal index was calculated to provide corrected measures for continuous improvements in analytical quality. Results The Sigma metric was highest using the external quality assessment standards of China: it was sigma ≥6 or higher in 57.1% of plasma proteins. But Sigma metric was lower by using RiliBÄK or biological variation standards. IgG, C3 and C-reactive protein all required quality improvements in imprecision. A single-rule 13s for internal quality control was recommended for IgA, IgM, C4 and rheumatoid factor, whereas multiple rules (13s/22s/R4s) were recommended for IgG, C3 and C-reactive protein, according to the external quality assessment standards of China. Conclusions Different quality goals can lead to different Sigma metric for the same analyte. As the lowest acceptable standard in clinical practice, the external quality assessment standard of China can guide laboratories to formulate reasonable quality improvement programmes.
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Mortillaro, N. A., and A. E. Taylor. "Microvascular permeability to endogenous plasma proteins in the jejunum." American Journal of Physiology-Heart and Circulatory Physiology 258, no. 6 (1990): H1650—H1654. http://dx.doi.org/10.1152/ajpheart.1990.258.6.h1650.
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Steady-state lymph flow and lymph (CL) and plasma (CP) protein concentrations were measured at venous outflow pressures of 0, 10, 20, and 30 mmHg in an autoperfused segment of cat jejunum. In addition to determining total protein concentrations in lymph and plasma, polyacrylamide gradient gel electrophoresis was used to determine lymph and plasma protein concentrations of albumin and nine other plasma proteins. The osmotic reflection coefficient (sigma d) for total proteins, albumin, and each of the nine protein fractions was estimated using CL/CP at a capillary filtration rate independent state, when 1 - CL/CP = sigma d. A sigma d of 0.83 was obtained for total proteins, a value similar to that reported for both dog jejunum and descending colon (0.85) but appreciably different from that reported for both cat stomach (0.78) and ileum (0.92). Additionally, sigma d for albumin and each of the nine plasma protein fractions (molecular radii ranging from 37 to 120 A) increased as molecular radius increased. A two-pore model composed of a ratio of 3,750 48-A radius small pores to one 250-A radius large pore describes the data obtained, with 82% of the total volume flow occurring through the small pores and 16% through the large pores.