Vps9p is a guanine nucleotide exchange factor involved in vesicle- mediated vacuolar protein transport

Hiroko Hama, Gregory G. Tall, Bruce F Horazdovsky

Research output: Contribution to journalArticle

114 Citations (Scopus)

Abstract

Vacuolar protein sorting (vps) mutants of Saccharomyces cerevisiae missort and secrete vacuolar hydrolases. The gene affected in one of these mutants, VPS21, encodes a member of the Sec4/Ypt/Rab family of small GTPases. Rab proteins play an essential role in vesicle-mediated protein transport. Using both yeast two-hybrid assays and chemical cross-linking, we have identified another VPS gene product, Vps9p, that preferentially interacts with a mutant form of Vps21p-S21N that binds GDP but not GTP. In vitro purified Vps9p was found to stimulate GDP release from Vps21p in a dose- dependent manner. Vps9p also stimulated GTP association as a result of facilitated GDP release. However, Vps9p did not stimulate guanine nucleotide exchange of GTP-bound Vps21p or GTP hydrolysis. We tested the ability of Vps9p to stimulate the intrinsic guanine nucleotide exchange activity of Rab5, which is a mammalian sequence homologue of Vps21p, and Ypt7p, which is another yeast Rab protein involved in vacuolar protein transport. Rab5, but not Ypt7p was responsive to Vps9p, which indicates that Vps9p recognizes sequence variation among Rab proteins. We conclude that Vps9p is a novel guanine nucleotide exchange factor that is specific for Vps21p/Rab5. Since there are no obvious Vps9p sequence homologues in yeast, Vps9p may also possess unique regulatory functions required for vacuolar protein transport.

Original languageEnglish (US)
Pages (from-to)15284-15291
Number of pages8
JournalJournal of Biological Chemistry
Volume274
Issue number21
DOIs
StatePublished - May 21 1999
Externally publishedYes

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Guanine Nucleotide Exchange Factors
Protein Transport
Guanosine Triphosphate
Guanine Nucleotides
Sequence Homology
Yeast
Proteins
Two-Hybrid System Techniques
Fungal Proteins
Monomeric GTP-Binding Proteins
Hydrolases
Genes
Saccharomyces cerevisiae
Hydrolysis
Yeasts
Sorting
Assays
Association reactions

ASJC Scopus subject areas

  • Biochemistry

Cite this

Vps9p is a guanine nucleotide exchange factor involved in vesicle- mediated vacuolar protein transport. / Hama, Hiroko; Tall, Gregory G.; Horazdovsky, Bruce F.

In: Journal of Biological Chemistry, Vol. 274, No. 21, 21.05.1999, p. 15284-15291.

Research output: Contribution to journalArticle

Hama, Hiroko ; Tall, Gregory G. ; Horazdovsky, Bruce F. / Vps9p is a guanine nucleotide exchange factor involved in vesicle- mediated vacuolar protein transport. In: Journal of Biological Chemistry. 1999 ; Vol. 274, No. 21. pp. 15284-15291.
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