Ustilago maydis KP6 killer toxin: structure, expression in Saccharomyces cerevisiae, and relationship to other cellular toxins

1990 ◽  
Vol 10 (4) ◽  
pp. 1373-1381
Author(s):  
J Tao ◽  
I Ginsberg ◽  
N Banerjee ◽  
W Held ◽  
Y Koltin ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Fungal Pathogen ◽  
Secretory Pathway ◽  
Rna Virus ◽  
Killer Toxin ◽  
Ustilago Maydis ◽  
Cleavage Sites ◽  
Double Stranded Rna ◽  
Killer Toxins ◽  
Covalently Linked

There are a number of yeasts that secrete killer toxins, i.e., proteins lethal to sensitive cells of the same or related species. Ustilago maydis, a fungal pathogen of maize, also secretes killer toxins. The best characterized of the U. maydis killer toxins is the KP6 toxin, which consists of two small polypeptides that are not covalently linked. In this work, we show that both are encoded by one segment of the genome of a double-stranded RNA virus. They are synthesized as a preprotoxin that is processed in a manner very similar to that of the Saccharomyces cerevisiae k1 killer toxin, also encoded by a double-strand RNA virus. Active U. maydis KP6 toxin was secreted from S. cerevisiae transformants expressing the KP6 preprotoxin. The two secreted polypeptides were not glycosylated in U. maydis, but one was glycosylated in S. cerevisiae. Comparison of known and predicted cleavage sites among the five killer toxins of known sequence established a three-amino-acid specificity for a KEX2-like enzyme and predicted a new, undescribed processing enzyme in the secretory pathway in the fungi. The mature KP6 toxin polypeptides had hydrophobicity profiles similar to those of other known cellular toxins.

scholarly journals Ustilago maydis KP6 killer toxin: structure, expression in Saccharomyces cerevisiae, and relationship to other cellular toxins.

1990 ◽  
Vol 10 (4) ◽  
pp. 1373-1381 ◽  
Author(s):  
J Tao ◽  
I Ginsberg ◽  
N Banerjee ◽  
W Held ◽  
Y Koltin ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Fungal Pathogen ◽  
Secretory Pathway ◽  
Rna Virus ◽  
Killer Toxin ◽  
Ustilago Maydis ◽  
Cleavage Sites ◽  
Double Stranded Rna ◽  
Killer Toxins ◽  
Covalently Linked

There are a number of yeasts that secrete killer toxins, i.e., proteins lethal to sensitive cells of the same or related species. Ustilago maydis, a fungal pathogen of maize, also secretes killer toxins. The best characterized of the U. maydis killer toxins is the KP6 toxin, which consists of two small polypeptides that are not covalently linked. In this work, we show that both are encoded by one segment of the genome of a double-stranded RNA virus. They are synthesized as a preprotoxin that is processed in a manner very similar to that of the Saccharomyces cerevisiae k1 killer toxin, also encoded by a double-strand RNA virus. Active U. maydis KP6 toxin was secreted from S. cerevisiae transformants expressing the KP6 preprotoxin. The two secreted polypeptides were not glycosylated in U. maydis, but one was glycosylated in S. cerevisiae. Comparison of known and predicted cleavage sites among the five killer toxins of known sequence established a three-amino-acid specificity for a KEX2-like enzyme and predicted a new, undescribed processing enzyme in the secretory pathway in the fungi. The mature KP6 toxin polypeptides had hydrophobicity profiles similar to those of other known cellular toxins.

The coat protein of the yeast double-stranded RNA virus L-A attaches covalently to the cap structure of eukaryotic mRNA

1992 ◽  
Vol 12 (8) ◽  
pp. 3390-3398
Author(s):  
A Blanc ◽  
C Goyer ◽  
N Sonenberg
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Coat Protein ◽  
Translation Initiation ◽  
Rna Virus ◽  
Binding Protein ◽  
Covalent Bond ◽  
Cellular Proteins ◽  
Double Stranded Rna ◽  
Virus Coat ◽  
Drosophila Cells

The eukaryotic mRNA 5' cap structure m7GpppX (where X is any nucleotide) interacts with a number of cellular proteins. Several of these proteins were studied in mammalian, yeast, and drosophila cells and found to be involved in translation initiation. Here we describe a novel cap-binding protein, the coat protein of L-A, a double-stranded RNA virus that is persistently maintained in many Saccharomyces cerevisiae strains. The results also suggest that the coat protein of a related double-stranded RNA virus (L-BC) is likewise a cap-binding protein. Strikingly, in contrast to the cellular cap-binding proteins, the interaction between the L-A virus coat protein and the cap structure is through a covalent bond.

scholarly journals Functions of Conserved Motifs in the RNA-Dependent RNA Polymerase of a Yeast Double-Stranded RNA Virus

1998 ◽  
Vol 72 (5) ◽  
pp. 4427-4429 ◽  
Author(s):  
Eric Routhier ◽  
Jeremy A. Bruenn
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Polymerase ◽  
Rna Virus ◽  
Rna Dependent Rna Polymerase ◽  
Conserved Motifs ◽  
Double Stranded Rna ◽  
Conserved Regions

ABSTRACT At least eight conserved motifs are visible in the totivirus RNA-dependent RNA polymerase (RDRP). We have systematically altered each of these in the Saccharomyces cerevisiaedouble-stranded RNA virus ScVL1 by substituting the conserved motifs from a giardiavirus. The results help define the conserved regions of the RDRP involved in polymerase function and those essential for other reasons.

Killer Toxins of Yeasts: Inhibitors of Fermentation and Their Adsorption

1987 ◽  
Vol 50 (3) ◽  
pp. 234-238 ◽  
Author(s):  
FERDINAND RADLER ◽  
MANFRED SCHMITT
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Wall ◽  
Yeast Cell ◽  
Cell Walls ◽  
Killer Toxin ◽  
Yeast Cells ◽  
Toxin Concentration ◽  
Commercial Preparation ◽  
Killer Toxins ◽  
Original Amount

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.

α-Synuclein inhibits Snx3-retromer retrograde trafficking of the conserved membrane-bound proprotein convertase Kex2 in the secretory pathway of Saccharomyces cerevisiae

2021 ◽  
Author(s):  
Santhanasabapathy Rajasekaran ◽  
Patricia P Peterson ◽  
Zhengchang Liu ◽  
Lucy C Robinson ◽  
Stephan N Witt
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Secretory Pathway ◽  
Killer Toxin ◽  
Alpha Synuclein ◽  
Proprotein Convertase ◽  
Retrograde Trafficking ◽  
Sorting Nexin ◽  
Late Endosomes ◽  
Membrane Bound ◽  
Dipeptidyl Aminopeptidase

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.

Double-stranded RNAs that encode killer toxins in Saccharomyces cerevisiae: unstable size of M double-stranded RNA and inhibition of M2 replication by M1

1984 ◽  
Vol 4 (9) ◽  
pp. 1747-1753
Author(s):  
S S Sommer ◽  
R B Wickner
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Size Variation ◽  
Double Stranded Rna ◽  
Killer Toxins ◽  
Enhanced Degradation

The sizes of M1 and M2 (but not L) change rapidly with growth, varying by perhaps as much as 33%. Size variation is seen within 76 generations. In addition, the exclusion of M2 by M1 or L-A-E [( EXL]) is mediated by inhibition of replication or segregation, not by enhanced degradation of preexisting molecules.

scholarly journals Immunolocalization of Kex2 protease identifies a putative late Golgi compartment in the yeast Saccharomyces cerevisiae.

1991 ◽  
Vol 113 (3) ◽  
pp. 527-538 ◽  
Author(s):  
K Redding ◽  
C Holcomb ◽  
R S Fuller
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Secretory Pathway ◽  
Killer Toxin ◽  
Proteolytic Processing ◽  
Yeast Cells ◽  
Yeast Saccharomyces Cerevisiae ◽  
Golgi Compartment ◽  
Membrane Bound ◽  
Gene Structures ◽  
Stage Analysis

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.

scholarly journals Double-stranded RNAs that encode killer toxins in Saccharomyces cerevisiae: unstable size of M double-stranded RNA and inhibition of M2 replication by M1.

1984 ◽  
Vol 4 (9) ◽  
pp. 1747-1753 ◽  
Author(s):  
S S Sommer ◽  
R B Wickner
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Size Variation ◽  
Double Stranded Rna ◽  
Killer Toxins ◽  
Enhanced Degradation

The sizes of M1 and M2 (but not L) change rapidly with growth, varying by perhaps as much as 33%. Size variation is seen within 76 generations. In addition, the exclusion of M2 by M1 or L-A-E [( EXL]) is mediated by inhibition of replication or segregation, not by enhanced degradation of preexisting molecules.

scholarly journals Killer systems in Saccharomyces cerevisiae: three distinct modes of exclusion of M2 double-stranded RNA by three species of double-stranded RNA, M1, L-A-E, and L-A-HN.

1983 ◽  
Vol 3 (4) ◽  
pp. 654-661 ◽  
Author(s):  
R B Wickner
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Killer Toxin ◽  
Mendelian Inheritance ◽  
Double Stranded Rna ◽  
Heat Curing ◽  
Natural Variants

M1 and M2 double-stranded RNAs (dsRNAs) code for the K1R1 and K2R2 killer toxin and resistance functions, respectively. Natural variants of a larger dsRNA (L-A) carry various combinations of the [EXL], [HOK], and [NEX] genes, which affect the K1 and K2 killer systems. Other dsRNAs, the same size as L-A, called L-B and L-C, are often present with L-A. We show that K1 killer strains have [HOK] and [NEX] but not [EXL] on their L-A (in disagreement with Field et al., Cell 31:193-200, 1982). These strains also carry other L-size molecules detectable after heat-curing has eliminated L-A. The exclusion of M2 dsRNA observed on mating K2 strains with K1 strains is due to the M1 dsRNA (not the L-A dsRNA as claimed by Field et al.) in the K1 strains. Four independent mutants of a [KIL-k2] [NEX-o] [HOK-o] strain were selected for resistance to [EXL] exclusion of M2 ([EXLR] phenotype). The [EXLR] phenotype showed non-Mendelian inheritance in each case, and these mutants had simultaneously each acquired [HOK]. The mutations were located on L-A and not on M2, and did not confer resistance to M1 exclusion of M2.

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