Sec2p Mediates Nucleotide Exchange on Sec4p and
 Is Involved in Polarized Delivery of Post-Golgi Vesicles

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Abstract

The small GTPase Sec4p is required for vesicular transport at the post-Golgi stage of yeast secretion. Here we present evidence that mutations in SEC2, itself an essential gene that acts at the same stage of the secretory pathway, cause Sec4p to mislocalize as a result of a random rather than a polarized accumulation of vesicles. Sec2p and Sec4p interact directly, with the nucleotide-free conformation of Sec4p being the preferred state for interaction with Sec2p. Sec2p functions as an exchange protein, catalyzing the dissociation of GDP from Sec4 and promoting the binding of GTP. We propose that Sec2p functions to couple the activation of Sec4p to the polarized delivery of vesicles to the site of exocytosis.

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Author and article information

Journal

Journal ID (nlm-ta): J Cell Biol

Title: The Journal of Cell Biology

Publisher: The Rockefeller University Press

ISSN (Print): 0021-9525

ISSN (Electronic): 1540-8140

Publication date (Print): 30 June 1997

Volume: 137

Issue: 7

Pages: 1495-1509

Affiliations

Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510

Article

DOI: 10.1083/jcb.137.7.1495

PMC ID: 2137815

PubMed ID: 9199166

SO-VID: 968e6d94-9c28-458f-ab4a-aa6f9b83e262

History

Date received : 21 March 1997

Date revision received : 1 May 1997

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