Localization of components involved in protein transport and processing through the yeast Golgi apparatus

Alex Franzusoff, Kevin Edward Redding, Jeff Crosby, Robert S. Fuller, Randy Schekman

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Saccharomyces cerevisiae sec7 mutants exhibit pleiotropic deficiencies in the transit of proteins through the Golgi apparatus, and elaborate an array of Golgi apparatus-like cisternae at a restrictive growth temperature (37°C). The SEC7 gene encodes an essential high-molecular weight protein (227 kD) that is phosphorylated in vivo. In cell lysates, Sec7 protein (Sec7p) is recovered in both sedimentable and soluble fractions. A punctate immunofluorescent pattern of Sec7p-associated structures seen in SEC cells coalesces in sec14 mutant yeast that accumulate exaggerated Golgi cisternae at 37°C. Sec7p may function as a peripheral membrane protein that cycles between a soluble, cytosolic pool and a sedimentable, membraneassociated complex for its essential role in vesicular traffic through the Golgi apparatus. The transmembrane Kex2 protease, which processes precursors of secreted peptides within the yeast secretory pathway, is also localized by indirect immunofluorescence to multiple structures in the yeast cell (Redding, K., and R. Fuller, manuscript submitted for publication). In double-immunofluorescence labeling experiments, significant colocalization of Sec7 and Kex2 proteins was found. Colocalization of the two antigens, one implicated in protein transport through the Golgi apparatus and the other in processing within a late Golgi compartment, supports the conclusion that we have visualized the yeast Golgi apparatus.

Original languageEnglish
Pages (from-to)27-37
Number of pages11
JournalJournal of Cell Biology
Issue number1
Publication statusPublished - Jan 1991


ASJC Scopus subject areas

  • Cell Biology

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