title: In vitro protein translocation across the yeast endoplasmic reticulum: ATP-dependent posttranslational translocation of the prepro-alpha-factor.
abstract: The in vitro synthesized precursor of the alpha-factor pheromone, prepro-alpha-factor, of Saccharomyces cerevisiae was translocated across yeast microsomal membranes in either a homologous or a wheat germ cell free system. Translocated prepro-alpha-factor was glycosylated, sedimented with yeast microsomal vesicles, and was protected from digestion by added protease, but was soluble after alkaline sodium carbonate treatment. Thus prepro-alpha-factor was properly sequestered within yeast microsomal vesicles, but was not integrated into the lipid bilayer. In marked contrast to protein translocation across mammalian microsomal membranes, translocation of prepro-alpha-factor across yeast microsomal membranes could occur posttranslationally. This reaction required protein components in the yeast microsomal fraction that could be inactivated by alkylation or proteolysis, was ATP-dependent, and was insensitive to the presence of a variety of uncouplers and ionophores.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D002474:Cell-Free System; D004285:Dogs; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D000072235:Mating Factor; D010455:Peptides / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D012261:Ribonucleoproteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D018271:Signal Recognition Particle
chemical_list: D005656:Fungal Proteins; D010455:Peptides; D012261:Ribonucleoproteins; D018271:Signal Recognition Particle; D000072235:Mating Factor; D000255:Adenosine Triphosphate