| Title: | "Saccharomyces cerevisiae a-factor mutants reveal residues critical for processing, activity, and export" |
| Author(s): | Huyer G; Kistler A; Nouvet FJ; George CM; Boyle ML; Michaelis S; |
| Address: | "Department of Cell Biology, The Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA" |
| ISSN/ISBN: | 1535-9778 (Print) 1535-9786 (Electronic) 1535-9786 (Linking) |
| Abstract: | "The Saccharomyces cerevisiae mating pheromone a-factor provides a paradigm for understanding the biogenesis of prenylated fungal pheromones. The biogenesis of a-factor involves multiple steps: (i) C-terminal CAAX modification (where C is cysteine, A is aliphatic, and X is any residue) which includes prenylation, proteolysis, and carboxymethylation (by Ram1p/Ram2p, Ste24p or Rce1p, and Ste14p, respectively); (ii) N-terminal processing, involving two sequential proteolytic cleavages (by Ste24p and Axl1p); and (iii) nonclassical export (by Ste6p). Once exported, mature a-factor interacts with the Ste3p receptor on MATalpha cells to stimulate mating. The a-factor biogenesis machinery is well defined, as is the CAAX motif that directs C-terminal modification; however, very little is known about the sequence determinants within a-factor required for N-terminal processing, activity, and export. Here we generated a large collection of a-factor mutants and identified residues critical for the N-terminal processing steps mediated by Ste24p and Axl1p. We also identified mutants that fail to support mating but do not affect biogenesis or export, suggesting a defective interaction with the Ste3p receptor. Mutants significantly impaired in export were also found, providing evidence that the Ste6p transporter recognizes sequence determinants as well as CAAX modifications. We also performed a phenotypic analysis of the entire set of isogenic a-factor biogenesis machinery mutants, which revealed information about the dependency of biogenesis steps upon one another, and demonstrated that export by Ste6p requires the completion of all processing events. Overall, this comprehensive analysis will provide a useful framework for the study of other fungal pheromones, as well as prenylated metazoan proteins involved in development and aging" |
| Keywords: | ATP-Binding Cassette Transporters/genetics/metabolism Amino Acid Substitution/genetics Binding Sites/genetics Biological Transport Endopeptidases/genetics/metabolism Glycoproteins/genetics/metabolism Lipoproteins/*biosynthesis/physiology Membrane Proteins; |
| Notes: | "MedlineHuyer, Gregory Kistler, Amy Nouvet, Franklin J George, Carolyn M Boyle, Meredith L Michaelis, Susan eng R01 GM041223/GM/NIGMS NIH HHS/ GM41223/GM/NIGMS NIH HHS/ Research Support, N.I.H., Extramural 2006/09/12 Eukaryot Cell. 2006 Sep; 5(9):1560-70. doi: 10.1128/EC.00161-06" |
