Biogenesis of the Saccharomyces cerevisiae mating pheromone a-factor

J Cell Biol. 1997 Jan 27;136(2):251-69. doi: 10.1083/jcb.136.2.251.

Abstract

The Saccharomyces cerevisiae mating pheromone a-factor is a prenylated and carboxyl methylated extracellular peptide signaling molecule. Biogenesis of the a-factor precursor proceeds via a distinctive multistep pathway that involves COOH-terminal modification. NH2-terminal proteolysis, and a nonclassical export mechanism. In this study, we examine the formation and fate of a-factor biosynthetic intermediates to more precisely define the events that occur during a-factor biogenesis. We have identified four distinct a-factor biosynthetic intermediates (P0, P1, P2, and M) by metabolic labeling, immunoprecipitation, and SDS-PAGE. We determined the biochemical composition of each by defining their NH2-terminal amino acid and COOH-terminal modification status. Unexpectedly, we discovered that not one, but two NH2-terminal cleavage steps occur during the biogenesis of a-factor. In addition, we have shown that COOH-terminal prenylation is required for the NH2-terminal processing of a-factor and that all the prenylated a-factor intermediates (P1, P2, and M) are membrane bound, suggesting that many steps of a-factor biogenesis occur in association with membranes. We also observed that although the biogenesis of a-factor is a rapid process, it is inherently inefficient, perhaps reflecting the potential for regulation. Previous studies have identified gene products that participate in the COOH-terminal modification (Ram1p, Ram2p, Ste14p), NH2-terminal processing (Ste24p, Axl1p), and export (Ste6p) of a-factor. The intermediates defined in the present study are discussed in the context of these biogenesis components to formulate an overall model for the pathway of a-factor biogenesis.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Biological Transport
  • Fungal Proteins / biosynthesis
  • Fungal Proteins / chemistry
  • Fungal Proteins / metabolism
  • Kinetics
  • Lipoproteins / biosynthesis
  • Lipoproteins / chemistry
  • Lipoproteins / metabolism*
  • Methylation
  • Molecular Sequence Data
  • Pheromones / biosynthesis
  • Pheromones / chemistry
  • Pheromones / metabolism*
  • Protein Precursors / biosynthesis
  • Protein Precursors / chemistry
  • Protein Precursors / metabolism*
  • Protein Prenylation
  • Protein Processing, Post-Translational*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins
  • Species Specificity

Substances

  • Fungal Proteins
  • Lipoproteins
  • MFA2 protein, S cerevisiae
  • Pheromones
  • Protein Precursors
  • Saccharomyces cerevisiae Proteins