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J Cell Biol

Title:		Biogenesis of the Saccharomyces cerevisiae mating pheromone a-factor
Author(s):		Chen P; Sapperstein SK; Choi JD; Michaelis S;
Address:		"Department of Cell Biology and Anatomy, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA"
Journal Title:		J Cell Biol
Year:		1997
Volume:		136
Issue:		2
Page Number:		251 - 269
DOI:		10.1083/jcb.136.2.251
ISSN/ISBN:		0021-9525 (Print) 1540-8140 (Electronic) 0021-9525 (Linking)
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"
Keywords:		Amino Acid Sequence Biological Transport Fungal Proteins/biosynthesis/chemistry/metabolism Kinetics Lipoproteins/biosynthesis/chemistry/*metabolism Methylation Molecular Sequence Data Pheromones/biosynthesis/chemistry/*metabolism Protein Precursors/biosyn;
Notes:		"MedlineChen, P Sapperstein, S K Choi, J D Michaelis, S eng GM41223/GM/NIGMS NIH HHS/ Research Support, U.S. Gov't, P.H.S. 1997/01/27 J Cell Biol. 1997 Jan 27; 136(2):251-69. doi: 10.1083/jcb.136.2.251"