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Journal articles on the topic 'K9 type yeast killer toxin'

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Published: 4 June 2021
Last updated: 15 February 2022

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1

Soares, Giselle A. M., and Hélia H. Sato. "Killer toxin of Saccharomyces cerevisiae Y500-4L active against Fleischmann and Itaiquara commercial brands of yeast." Revista de Microbiologia 30, no. 3 (July 1999): 253–57. http://dx.doi.org/10.1590/s0001-37141999000300012.

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The strain Saccharomyces cerevisiae Y500-4L, previously selected from the must of alcohol producing plants and showing high fermentative and killer capacities, was characterized according to the interactions between the yeasts and examined for curing and detection of dsRNA plasmids, which code for the killer character. The killer yeast S. cerevisiae Y500-4L showed considerable killer activity against the Fleischmann and Itaiquara commercial brands of yeast and also against the standard killer yeasts K2 (S. diastaticus NCYC 713), K4 (Candida glabrata NCYC 388) and K11 (Torulopsis glabrata ATCC 15126). However S. cerevisiae Y500-4L showed sensitivity to the killer toxin produced by the standard killer yeasts K8 (Hansenula anomala NCYC 435), K9 (Hansenula mrakii NCYC 500), K10 (Kluyveromyces drosophilarum NCYC 575) and K11 (Torulopsis glabrata ATCC 15126). No M-dsRNA plasmid was detected in the S. cerevisiae Y500-4L strain and these results suggest that the genetic basis for toxin production is encoded by chromosomal DNA. The strain S. cerevisiae Y500-4L was more resistant to the loss of the phenotype killer with cycloheximide and incubation at elevated temperatures (40oC) than the standard killer yeast S. cerevisiae K1.
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2

RADLER, FERDINAND, and MANFRED SCHMITT. "Killer Toxins of Yeasts: Inhibitors of Fermentation and Their Adsorption." Journal of Food Protection 50, no. 3 (March 1, 1987): 234–38. http://dx.doi.org/10.4315/0362-028x-50.3.234.

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The killer toxin (KT 28), a glycoprotein of Saccharomyces cerevisiae strain 28, was almost completely adsorbed by bentonite, when applied at a concentration of 1 g per liter. No significant differences were found between several types of bentonite. Killer toxin KT 28 is similarly adsorbed by intact yeast cells or by a commercial preparation of yeast cell walls that has been recommended to prevent stuck fermentations. An investigation of the cell wall fractions revealed that the toxin KT 28 was mainly adsorbed by mannan, that removed the toxin completely. The alkali-soluble and the alkali-insoluble β-1,3- and β-1,6-D-glucans lowered the toxin concentration to one tenth of the original amount. The killer toxin of the type K1 of S. cerevisiae was adsorbed much better by glucans than by mannan.
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3

IZGÜ, Fatih, Demet ALTINBAY, and Abdullah SERTKAYA. "Enzymic Activity of the K5-Type Yeast Killer Toxin and Its Characterization." Bioscience, Biotechnology, and Biochemistry 69, no. 11 (January 2005): 2200–2206. http://dx.doi.org/10.1271/bbb.69.2200.

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4

Hong, Z., P. Mann, N. H. Brown, L. E. Tran, K. J. Shaw, R. S. Hare, and B. DiDomenico. "Cloning and characterization of KNR4, a yeast gene involved in (1,3)-beta-glucan synthesis." Molecular and Cellular Biology 14, no. 2 (February 1994): 1017–25. http://dx.doi.org/10.1128/mcb.14.2.1017.

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k9 killer toxin from Hansenula mrakii was used to select a number of resistant mutants from Saccharomyces cerevisiae. Preliminary biochemical and genetic studies showed that some of them acquired structural defects in the cell wall. One of these mutants, the knr4-1 mutant, displays a number of cell wall defects, including osmotic sensitivity; sensitivity to cercosporamide, a known antifungal agent; and resistance to Zymolyase, a (1,3)-beta-glucanase. We report here the isolation and analysis of the KNR4 gene. DNA sequence analysis revealed an uninterrupted open reading frame which contains five potential start codons. The longest coding template encodes a protein of 505 amino acids with a calculated molecular mass of 57,044 Da. A data base search revealed 100% identity with a nuclear protein, SMI1p. Disruption of the KNR4 locus does not result in cell death; however, it leads to reduced levels of both (1,3)-beta-glucan synthase activity and (1,3)-beta-glucan content in the cell wall. The gene was mapped to the right arm of chromosome VII.
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5

Hong, Z., P. Mann, N. H. Brown, L. E. Tran, K. J. Shaw, R. S. Hare, and B. DiDomenico. "Cloning and characterization of KNR4, a yeast gene involved in (1,3)-beta-glucan synthesis." Molecular and Cellular Biology 14, no. 2 (February 1994): 1017–25. http://dx.doi.org/10.1128/mcb.14.2.1017-1025.1994.

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k9 killer toxin from Hansenula mrakii was used to select a number of resistant mutants from Saccharomyces cerevisiae. Preliminary biochemical and genetic studies showed that some of them acquired structural defects in the cell wall. One of these mutants, the knr4-1 mutant, displays a number of cell wall defects, including osmotic sensitivity; sensitivity to cercosporamide, a known antifungal agent; and resistance to Zymolyase, a (1,3)-beta-glucanase. We report here the isolation and analysis of the KNR4 gene. DNA sequence analysis revealed an uninterrupted open reading frame which contains five potential start codons. The longest coding template encodes a protein of 505 amino acids with a calculated molecular mass of 57,044 Da. A data base search revealed 100% identity with a nuclear protein, SMI1p. Disruption of the KNR4 locus does not result in cell death; however, it leads to reduced levels of both (1,3)-beta-glucan synthase activity and (1,3)-beta-glucan content in the cell wall. The gene was mapped to the right arm of chromosome VII.
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6

Lukša, Juliana, Monika Podoliankaitė, Iglė Vepštaitė, Živilė Strazdaitė-Žielienė, Jaunius Urbonavičius, and Elena Servienė. "Yeast β-1,6-Glucan Is a Primary Target for the Saccharomyces cerevisiae K2 Toxin." Eukaryotic Cell 14, no. 4 (February 20, 2015): 406–14. http://dx.doi.org/10.1128/ec.00287-14.

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ABSTRACTCertainSaccharomyces cerevisiaestrains secrete different killer proteins of double-stranded-RNA origin. These proteins confer a growth advantage to their host by increasing its survival. K2 toxin affects the target cell by binding to the cell surface, disrupting the plasma membrane integrity, and inducing ion leakage. In this study, we determined that K2 toxin saturates the yeast cell surface receptors in 10 min. The apparent amount of K2 toxin, bound to a single cell of wild type yeast under saturating conditions, was estimated to be 435 to 460 molecules. It was found that an increased level of β-1,6-glucan directly correlates with the number of toxin molecules bound, thereby impacting the morphology and determining the fate of the yeast cell. We observed that the binding of K2 toxin to the yeast surface receptors proceeds in a similar manner as in case of the related K1 killer protein. It was demonstrated that the externally supplied pustulan, a poly-β-1,6-glucan, but not the glucans bearing other linkage types (such as laminarin, chitin, and pullulan) efficiently inhibits the K2 toxin killing activity. In addition, the analysis of toxin binding to the intact cells and spheroplasts confirmed that majority of K2 protein molecules attach to the β-1,6-glucan, rather than the plasma membrane-localized receptors. Taken together, our results reveal that β-1,6-glucan is a primary target of K2 toxin and is important for the execution of its killing property.
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7

Miyamoto, Masahiko, Naohiko Onozato, Dakshnamurthy Selvakumar, Tetsuya Kimura, Yasuhiro Furuichi, and Tadazumi Komiyama. "The role of the histidine-35 residue in the cytocidal action of HM-1 killer toxin." Microbiology 152, no. 10 (October 1, 2006): 2951–58. http://dx.doi.org/10.1099/mic.0.29100-0.

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Diethylpyrocarbonate modification and site-directed mutagenesis studies of histidine-35 in HM-1 killer toxin (HM-1) have shown that a specific feature, the imidazole side chain of histidine-35, is essential for the expression of the killing activity. In subcellular localization experiments, wild-type HM-1 was in the membrane fraction of Saccharomyces cerevisiae BJ1824, but not the HM-1 analogue in which histidine-35 was replaced by alanine (H35A HM-1). Neither wild-type nor H35A HM-1 was detected in cellular fractions of HM-1-resistant yeast S. cerevisiae BJ1824 rhk1Δ : : URA3 and HM-1-insensitive yeast Candida albicans even after 1 h incubation. H35A HM-1 inhibited the activity of partially purified 1,3-β-glucan synthase from S. cerevisiae A451, and its extent was almost the same as wild-type HM-1. Co-immunoprecipitation experiments showed that wild-type and H35A HM-1 directly interact with the 1,3-β-glucan synthase complex. These results strongly suggest that histidine-35 has an important role in the cytocidal action of HM-1 that participates in the binding process to the HM-1 receptor protein on the cell membrane, but it is not essential for the interaction with, and inhibition of, 1,3-β-glucan synthase.
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8

Meškauskas, A., and D. Čitavičius. "The K2-type killer toxin- and immunity-encoding region from Saccharomyces cerevisiae: structure and expression in yeast." Gene 111, no. 1 (February 1992): 135–39. http://dx.doi.org/10.1016/0378-1119(92)90615-v.

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9

Suzuki, C., and S. Nikkuni. "The primary and subunit structure of a novel type killer toxin produced by a halotolerant yeast, Pichia farinosa." Journal of Biological Chemistry 269, no. 4 (January 1994): 3041–46. http://dx.doi.org/10.1016/s0021-9258(17)42044-8.

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10

Vepštaitė-Monstavičė, Iglė, Juliana Lukša, Aleksandras Konovalovas, Dovilė Ežerskytė, Ramunė Stanevičienė, Živilė Strazdaitė-Žielienė, Saulius Serva, and Elena Servienė. "Saccharomyces paradoxus K66 Killer System Evidences Expanded Assortment of Helper and Satellite Viruses." Viruses 10, no. 10 (October 16, 2018): 564. http://dx.doi.org/10.3390/v10100564.

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The Saccharomycetaceae yeast family recently became recognized for expanding of the repertoire of different dsRNA-based viruses, highlighting the need for understanding of their cross-dependence. We isolated the Saccharomyces paradoxus AML-15-66 killer strain from spontaneous fermentation of serviceberries and identified helper and satellite viruses of the family Totiviridae, which are responsible for the killing phenotype. The corresponding full dsRNA genomes of viruses have been cloned and sequenced. Sequence analysis of SpV-LA-66 identified it to be most similar to S. paradoxus LA-28 type viruses, while SpV-M66 was mostly similar to the SpV-M21 virus. Sequence and functional analysis revealed significant differences between the K66 and the K28 toxins. The structural organization of the K66 protein resembled those of the K1/K2 type toxins. The AML-15-66 strain possesses the most expressed killing property towards the K28 toxin-producing strain. A genetic screen performed on S. cerevisiae YKO library strains revealed 125 gene products important for the functioning of the S. paradoxus K66 toxin, with 85% of the discovered modulators shared with S. cerevisiae K2 or K1 toxins. Investigation of the K66 protein binding to cells and different polysaccharides implies the β-1,6 glucans to be the primary receptors of S. paradoxus K66 toxin. For the first time, we demonstrated the coherent habitation of different types of helper and satellite viruses in a wild-type S. paradoxus strain.
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11

Pagé, Nicolas, Manon Gérard-Vincent, Patrice Ménard, Maude Beaulieu, Masayuki Azuma, Gerrit J. P. Dijkgraaf, Huijuan Li, et al. "A Saccharomyces cerevisiae Genome-Wide Mutant Screen for Altered Sensitivity to K1 Killer Toxin." Genetics 163, no. 3 (March 1, 2003): 875–94. http://dx.doi.org/10.1093/genetics/163.3.875.

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Abstract Using the set of Saccharomyces cerevisiae mutants individually deleted for 5718 yeast genes, we screened for altered sensitivity to the antifungal protein, K1 killer toxin, that binds to a cell wall β-glucan receptor and subsequently forms lethal pores in the plasma membrane. Mutations in 268 genes, including 42 in genes of unknown function, had a phenotype, often mild, with 186 showing resistance and 82 hypersensitivity compared to wild type. Only 15 of these genes were previously known to cause a toxin phenotype when mutated. Mutants for 144 genes were analyzed for alkali-soluble β-glucan levels; 63 showed alterations. Further, mutants for 118 genes with altered toxin sensitivity were screened for SDS, hygromycin B, and calcofluor white sensitivity as indicators of cell surface defects; 88 showed some additional defect. There is a markedly nonrandom functional distribution of the mutants. Many genes affect specific areas of cellular activity, including cell wall glucan and mannoprotein synthesis, secretory pathway trafficking, lipid and sterol biosynthesis, and cell surface signal transduction, and offer new insights into these processes and their integration.
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12

Chen, Zhizhong, Hairong Zhang, Daniel Jablonowski, Xiaofeng Zhou, Xiaozhi Ren, Xuhui Hong, Raffael Schaffrath, Jian-Kang Zhu, and Zhizhong Gong. "Mutations in ABO1/ELO2, a Subunit of Holo-Elongator, Increase Abscisic Acid Sensitivity and Drought Tolerance in Arabidopsis thaliana." Molecular and Cellular Biology 26, no. 18 (September 15, 2006): 6902–12. http://dx.doi.org/10.1128/mcb.00433-06.

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ABSTRACT The phytohormone abscisic acid (ABA) plays an important role in modulating plant growth, development, and stress responses. In a genetic screen for mutants with altered drought stress responses, we identified an ABA-overly sensitive mutant, the abo1 mutant, which showed a drought-resistant phenotype. The abo1 mutation enhances ABA-induced stomatal closing and increases ABA sensitivity in inhibiting seedling growth. abo1 mutants are more resistant to oxidative stress than the wild type and show reduced levels of transcripts of several stress- or ABA-responsive genes. Interestingly, the mutation also differentially modulates the development and growth of adjacent guard cells. Map-based cloning identified ABO1 as a new allele of ELO2, which encodes a homolog of Saccharomyces cerevisiae Iki3/Elp1/Tot1 and human IκB kinase-associated protein. Iki3/Elp1/Tot1 is the largest subunit of Elongator, a multifunctional complex with roles in transcription elongation, secretion, and tRNA modification. Ecotopic expression of plant ABO1/ELO2 in a tot1/elp1Δ yeast Elongator mutant complements resistance to zymocin, a yeast killer toxin complex, indicating that ABO1/ELO2 substitutes for the toxin-relevant function of yeast Elongator subunit Tot1/Elp1. Our results uncover crucial roles for ABO1/ELO2 in modulating ABA and drought responses in Arabidopsis thaliana.
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13

Brown, J. L., Z. Kossaczka, B. Jiang, and H. Bussey. "A mutational analysis of killer toxin resistance in Saccharomyces cerevisiae identifies new genes involved in cell wall (1-->6)-beta-glucan synthesis." Genetics 133, no. 4 (April 1, 1993): 837–49. http://dx.doi.org/10.1093/genetics/133.4.837.

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Abstract Recessive mutations leading to killer resistance identify the KRE9, KRE10 and KRE11 genes. Mutations in both the KRE9 and KRE11 genes lead to reduced levels of (1-->6)-beta-glucan in the yeast cell wall. The KRE11 gene encodes a putative 63-kD cytoplasmic protein, and disruption of the KRE11 locus leads to a 50% reduced level of cell wall (1-->6)-glucan. Structural analysis of the (1-->6)-beta-glucan remaining in a kre11 mutant indicates a polymer smaller in size than wild type, but containing a similar proportion of (1-->6)- and (1-->3)-linkages. Genetic interactions among cells harboring mutations at the KRE11, KRE6 and KRE1 loci indicate lethality of kre11 kre6 double mutants and that kre11 is epistatic to kre1, with both gene products required to produce the mature glucan polymer at wild-type levels. Analysis of these KRE genes should extend knowledge of the beta-glucan biosynthetic pathway, and of cell wall synthesis in yeast.
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14

Redding, K., C. Holcomb, and R. S. Fuller. "Immunolocalization of Kex2 protease identifies a putative late Golgi compartment in the yeast Saccharomyces cerevisiae." Journal of Cell Biology 113, no. 3 (May 1, 1991): 527–38. http://dx.doi.org/10.1083/jcb.113.3.527.

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The Kex2 protein of the yeast Saccharomyces cerevisiae is a membrane-bound, Ca2(+)-dependent serine protease that cleaves the precursors of the mating pheromone alpha-factor and the M1 killer toxin at pairs of basic residues during their transport through the secretory pathway. To begin to characterize the intracellular locus of Kex2-dependent proteolytic processing, we have examined the subcellular distribution of Kex2 protein in yeast by indirect immunofluorescence. Kex2 protein is located at multiple, discrete sites within wild-type yeast cells (average, 3.0 +/- 1.7/mother cell). Qualitatively similar fluorescence patterns are observed at elevated levels of expression, but no signal is found in cells lacking the KEX2 gene. Structures containing Kex2 protein are not concentrated at a perinuclear location, but are distributed throughout the cytoplasm at all phases of the cell cycle. Kex2-containing structures appear in the bud at an early, premitotic stage. Analysis of conditional secretory (sec) mutants demonstrates that Kex2 protein ordinarily progresses from the ER to the Golgi but is not incorporated into secretory vesicles, consistent with the proposed localization of Kex2 protein to the yeast Golgi complex.
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15

Colussi, Paul A., Charles A. Specht, and Christopher H. Taron. "Characterization of a Nucleus-Encoded Chitinase from the Yeast Kluyveromyces lactis." Applied and Environmental Microbiology 71, no. 6 (June 2005): 2862–69. http://dx.doi.org/10.1128/aem.71.6.2862-2869.2005.

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ABSTRACT Endogenous proteins secreted from Kluyveromyces lactis were screened for their ability to bind to or to hydrolyze chitin. This analysis resulted in identification of a nucleus-encoded extracellular chitinase (KlCts1p) with a chitinolytic activity distinct from that of the plasmid-encoded killer toxin α-subunit. Sequence analysis of cloned KlCTS1 indicated that it encodes a 551-amino-acid chitinase having a secretion signal peptide, an amino-terminal family 18 chitinase catalytic domain, a serine-threonine-rich domain, and a carboxy-terminal type 2 chitin-binding domain. The association of purified KlCts1p with chitin is stable in the presence of high salt concentrations and pH 3 to 10 buffers; however, complete dissociation and release of fully active KlCts1p occur in 20 mM NaOH. Similarly, secreted human serum albumin harboring a carboxy-terminal fusion with the chitin-binding domain derived from KlCts1p also dissociates from chitin in 20 mM NaOH, demonstrating the domain's potential utility as an affinity tag for reversible chitin immobilization or purification of alkaliphilic or alkali-tolerant recombinant fusion proteins. Finally, haploid K. lactis cells harboring a cts1 null mutation are viable but exhibit a cell separation defect, suggesting that KlCts1p is required for normal cytokinesis, probably by facilitating the degradation of septum-localized chitin.
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16

Hill, K., C. Boone, M. Goebl, R. Puccia, A. M. Sdicu, and H. Bussey. "Yeast KRE2 defines a new gene family encoding probable secretory proteins, and is required for the correct N-glycosylation of proteins." Genetics 130, no. 2 (February 1, 1992): 273–83. http://dx.doi.org/10.1093/genetics/130.2.273.

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Abstract We have cloned, sequenced and disrupted the KRE2 gene of Saccharomyces cerevisiae, identified by killer-resistant mutants with a defective cell wall receptor for the toxin. The KRE2 gene is close to PHO8 on chromosome 4, and encodes a predicted 49-kD protein, Kre2p, that probably enters the secretory pathway. Haploid cells carrying a disruption of the KRE2 locus grow more slowly than wild-type cells at 30 degrees, and fail to grow at 37 degrees. At 30 degrees, kre2 mutants showed altered N-linked glycosylation of proteins, as the average size of N-linked outer chains was reduced. We identified two other genes, YUR1 on chromosome 10, and KTR1 on chromosome 15, whose predicted products share 36% identity with Kre2p over more than 300 amino acid residues. Yur1p has an N-terminal signal sequence like Kre2p, while Ktr1p has a predicted topology consistent with a type 2 membrane protein. In all cases the conserved regions of these proteins appear to be on the lumenal side of secretory compartments, suggesting related function. KRE2, KTR1 and YUR1 define a new yeast gene family.
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17

Masison, D. C., A. Blanc, J. C. Ribas, K. Carroll, N. Sonenberg, and R. B. Wickner. "Decoying the cap- mRNA degradation system by a double-stranded RNA virus and poly(A)- mRNA surveillance by a yeast antiviral system." Molecular and Cellular Biology 15, no. 5 (May 1995): 2763–71. http://dx.doi.org/10.1128/mcb.15.5.2763.

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The major coat protein of the L-A double-stranded RNA virus of Saccharomyces cerevisiae covalently binds m7 GMP from 5' capped mRNAs in vitro. We show that this cap binding also occurs in vivo and that, while this activity is required for expression of viral information (killer toxin mRNA level and toxin production) in a wild-type strain, this requirement is suppressed by deletion of SKI1/XRN1/SEP1. We propose that the virus creates decapped cellular mRNAs to decoy the 5'-->3' exoribonuclease specific for cap- RNA encoded by XRN1. The SKI2 antiviral gene represses the copy numbers of the L-A and L-BC viruses and the 20S RNA replicon, apparently by specifically blocking translation of viral RNA. We show that SKI2, SKI3, and SKI8 inhibit translation of electroporated luciferase and beta-glucuronidase mRNAs in vivo, but only if they lack the 3' poly(A) structure. Thus, L-A decoys the SKI1/XRN1/SEP1 exonuclease directed at 5' uncapped ends, but translation of the L-A poly(A)- mRNA is repressed by Ski2,3,8p. The SKI2-SKI3-SKI8 system is more effective against cap+ poly(A)- mRNA, suggesting a (nonessential) role in blocking translation of fragmented cellular mRNAs.
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18

Conti, Giorgio, Walter Magliani, Stefania Conti, Lucia Nencioni, Rossella Sgarbanti, Anna Teresa Palamara, and Luciano Polonelli. "Therapeutic Activity of an Anti-Idiotypic Antibody-Derived Killer Peptide against Influenza A Virus Experimental Infection." Antimicrobial Agents and Chemotherapy 52, no. 12 (September 29, 2008): 4331–37. http://dx.doi.org/10.1128/aac.00506-08.

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ABSTRACT The in vitro and in vivo activities of a killer decapeptide (KP) against influenza A virus is described, and the mechanisms of action are suggested. KP represents the functional internal image of a yeast killer toxin that proved to exert antimicrobial and anti-human immunodeficiency virus type 1 (HIV-1) activities. Treatment with KP demonstrated a significant inhibitory activity on the replication of two strains of influenza A virus in different cell lines, as evaluated by hemagglutination, hemadsorption, and plaque assays. The complete inhibition of virus particle production and a marked reduction of the synthesis of viral proteins (membrane protein and hemagglutinin, in particular) were observed at a KP concentration of 4 μg/ml. Moreover, KP administered intraperitoneally at a dose of 100 μg/mice once a day for 10 days to influenza A/NWS/33 (H1N1) virus-infected mice improved the survival of the animals by 40% and significantly decreased the viral titers in their lungs. Overall, KP appears to be the first anti-idiotypic antibody-derived peptide that displays inhibitory activity and that has a potential therapeutic effect against pathogenic microorganisms, HIV-1, and influenza A virus by different mechanisms of action.
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19

Baev, Didi, Alberto Rivetta, Xuewei S. Li, Slavena Vylkova, Esther Bashi, Clifford L. Slayman, and Mira Edgerton. "Killing of Candida albicans by Human Salivary Histatin 5 Is Modulated, but Not Determined, by the Potassium Channel TOK1." Infection and Immunity 71, no. 6 (June 2003): 3251–60. http://dx.doi.org/10.1128/iai.71.6.3251-3260.2003.

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ABSTRACT Salivary histatin 5 (Hst 5), a potent toxin for the human fungal pathogen Candida albicans, induces noncytolytic efflux of cellular ATP, potassium, and magnesium in the absence of cytolysis, implicating these ion movements in the toxin's fungicidal activity. Hst 5 action on Candida resembles, in many respects, the action of the K1 killer toxin on Saccharomyces cerevisiae, and in that system the yeast plasma membrane potassium channel, Tok1p, has recently been reported to be a primary target of toxin action. The question of whether the Candida homologue of Saccharomyces Tok1p might be a primary target of Hst 5 action has now been investigated by disruption of the C. albicans TOK1 gene. The resultant strains (TOK1/tok1) and (tok1/tok1) were compared with wild-type Candida (TOK1/TOK1) for relative ATP leakage and killing in response to Hst 5. Patch-clamp measurements on Candida protoplasts were used to verify the functional deletion of Tok1p and to provide its first description in Candida. Tok1p is an outwardly rectifying, noisily gated, 40-pS channel, very similar to that described in Saccharomyces. Knockout of CaTOK1 (tok1/tok1) completely abolishes the currents and gating events characteristic of Tok1p. Also, knockout (tok1/tok1) increases residual viability of Candida after Hst 5 treatment to 27%, from 7% in the wild type, while the single allele deletion (TOK1/tok1) increases viability to 18%. Comparable results were obtained for Hst-induced ATP efflux, but quantitative features of ATP loss suggest that wild-type TOK1 genes function cooperatively. Overall, very substantial killing and ATP efflux are produced by Hst 5 treatment after complete knockout of wild-type TOK1, making clear that Tok1p channels are not the primary site of Hst 5 action, even though they do play a modulating role.
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20

Abu-Mejdad, Najwa Mohammed Jameel Ali, Adnan I. Al-Badran, Abdullah H. Al-Saadoon, and Mohammed Hussein Minati. "A new report on gene expression of three killer toxin genes with antimicrobial activity of two killer toxins in Iraq." Bulletin of the National Research Centre 44, no. 1 (September 18, 2020). http://dx.doi.org/10.1186/s42269-020-00418-5.

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Abstract Background The K1, K2, and K28 toxins are usually encoded by several cytoplasmically genetic satellite dsRNAs (M1, M2, and M28), which are encapsulated with virus-like particles (VLPs) and reliant on an additional assembly of assistant yeast viruses (L-A) for their reproduction and encapsidation. Ascomycetous yeast species that have these VLPs are especially attractive targets for finding killer toxins like proteins. This is because the organisms are known in producing a large variety of secondary metabolites and extracellular enzymes, which have medical importance as alternative drugs for resistance bacterial strains, particularly multi-resistance drugs (MRD). Results For the first time, 31 type strains of yeasts were tested for killer toxin production in Iraq via the measurement of gene expression of three killer toxin genes (M1, M2, and M28) within the mycovirus in yeasts. All the type strains gave an expression for the three killer toxins with variable levels. The highest expression was recorded for the killer toxin genes in Torulaspora delbrueckii followed by Wickerhamomyces anomalus. Determined antibacterial activity of two killer toxins appeared with high inhibition zone against pathogenic strains of bacteria. Cytotoxicity against human blood cells was not found. These results considered the first record of killer toxins isolated from type strains in Iraq. Conclusion The two typical strains Torulaspora delbrueckii and Wickerhamomyces anomalus showed the highest level of gene expression for the three killer toxins.
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21

Rajasekaran, Santhanasabapathy, Patricia P. Peterson, Zhengchang Liu, Lucy C. Robinson, and Stephan N. Witt. "α-Synuclein inhibits Snx3-retromer retrograde trafficking of the conserved membrane-bound proprotein convertase Kex2 in the secretory pathway of Saccharomyces cerevisiae." Human Molecular Genetics, September 27, 2021. http://dx.doi.org/10.1093/hmg/ddab284.

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Abstract We tested the ability of alpha-synuclein (α-syn) to inhibit Snx3-retromer mediated retrograde trafficking of Kex2 and Ste13 between late endosomes and the trans-Golgi (TGN) using a Saccharomyces cerevisiae model of Parkinson’s disease (PD). Kex2 and Ste13 are a conserved, membrane-bound proprotein convertase and dipeptidyl aminopeptidase, respectively, that process pro-α-factor and pro-killer toxin. Each of these proteins contains a cytosolic tail that binds to sorting nexin Snx3. Using a combination of techniques, including fluorescence microscopy, western blotting and a yeast mating assay, we found that α-syn disrupts Snx3-retromer trafficking of Kex2-GFP and GFP-Ste13 from the late endosome to the TGN, resulting in these two proteins transiting to the vacuole by default. Using three α-syn variants (A53T, A30P, and α-synΔC, which lacks residues 101–140), we further found that A53T and α-synΔC, but not A30P, reduce Snx3-retromer trafficking of Kex2-GFP, which is likely to be due to weaker binding of A30P to membranes. Degradation of Kex2 and Ste13 in the vacuole should result in the secretion of unprocessed, inactive forms of α-factor, which will reduce mating efficiency between MATa and MATα cells. We found that wild-type α-syn but not A30P significantly inhibited the secretion of α-factor. Collectively, our results support a model in which the membrane-binding ability of α-syn is necessary to disrupt Snx3-retromer retrograde recycling of these two conserved endopeptidases.
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