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Gene Review

YPT7  -  Rab family GTPase YPT7

Saccharomyces cerevisiae S288c

Synonyms: AST4, GTP-binding protein YPT7, VAM4, YM8270.02, YML001W
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High impact information on YPT7

  • YPT7 gene disruption did not impair cellular growth at temperatures ranging from 17 degrees C to 37 degrees C. ypt7 null mutants are characterized by highly fragmented vacuoles and differential defects of vacuolar protein transport and maturation [1].
  • As Ypt7 is one of many Rab GTPases, ubiquitin-proteasome regulation may be involved in membrane fusion elsewhere [2].
  • Accordingly, we propose that the Ccz1-Mon1 complex is critical for the Ypt7-dependent tethering/docking stage leading to the formation of a trans-SNARE complex and subsequent vacuole fusion [3].
  • In vitro homotypic fusion of yeast vacuoles occurs in three stages: priming, the Sec18 (NSF)-mediated changes that precede vacuole association; docking, the Ypt7 and SNARE-mediated pairing of vacuoles; and fusion, mediated by calmodulin/V0/t-SNARE interactions [4].
  • We propose that the class C-Vps complex both promotes Vps39-dependent nucleotide exchange on Ypt7 and, based on the work of Price et al., acts as a Ypt7 effector that tethers transport vesicles to the vacuole [5].

Biological context of YPT7


Anatomical context of YPT7

  • Here we show that mutations in VAM3 (vacuolar t-SNARE) and YPT7 (rab GTPase), which are required to direct protein and membrane delivery from prevacuolar endosomal compartments to the vacuole, dramatically increase/stabilize PtdIns(3)P levels in vivo by disrupting its turnover [11].
  • cDNAs representing nine small G protein genes encoding Ypt proteins from the green algae Volvox carteri (YptV) and Chlamydomonas reinhardtii (YptC) were tested for their ability to complement mutations in the YPT1, SEC4, and YPT7 genes of Saccharomyces cerevisiae strains defective in different steps of intracellular vesicle transport [12].
  • We report here that endocytosed pheromone alpha-factor accumulates in late endosomes in delta ypt7 cells, indicating that Ypt7p is involved in the regulation of transport steps from late endosomes to the vacuole [8].

Regulatory relationships of YPT7

  • In accord with this finding in the reconstituted fusion reaction, the inactivation of Ypt7p by the GTPase-activating protein Gyp1-46p only blocks the fusion of purified vacuoles when Yck3p is present and active [13].

Other interactions of YPT7

  • Here we present data indicating that CCZ1 is a close partner of the YPT7 gene, which encodes Rab GTPase and is required for fusion of transport vesicles to vacuole and homotypic vacuole fusion [14].
  • In accord with this finding, cells deleted for the gene encoding Ypt7 have normal amounts of Vam7p but have little Vam7p on their isolated vacuoles [15].
  • A previous study has shown that a large protein complex containing Vps39 and Vps41 functions as a downstream effector of the active, GTP-bound form of Ypt7, a rab GTPase required for the fusion of vesicular intermediates with the vacuole (Price, A., D. Seals, W. Wickner, and C. Ungermann. 2000. J. Cell Biol. 148:1231-1238) [5].
  • In Saccharomyces cerevisiae a protein complex of Mon1 and Ccz1 functions with the small GTPase Ypt7 to mediate vesicle trafficking to the vacuole [16].


  1. Endocytosis in yeast: evidence for the involvement of a small GTP-binding protein (Ypt7p). Wichmann, H., Hengst, L., Gallwitz, D. Cell (1992) [Pubmed]
  2. The ubiquitin-proteasome system regulates membrane fusion of yeast vacuoles. Kleijnen, M.F., Kirkpatrick, D.S., Gygi, S.P. EMBO J. (2007) [Pubmed]
  3. Yeast homotypic vacuole fusion requires the Ccz1-Mon1 complex during the tethering/docking stage. Wang, C.W., Stromhaug, P.E., Kauffman, E.J., Weisman, L.S., Klionsky, D.J. J. Cell Biol. (2003) [Pubmed]
  4. Ergosterol is required for the Sec18/ATP-dependent priming step of homotypic vacuole fusion. Kato, M., Wickner, W. EMBO J. (2001) [Pubmed]
  5. New component of the vacuolar class C-Vps complex couples nucleotide exchange on the Ypt7 GTPase to SNARE-dependent docking and fusion. Wurmser, A.E., Sato, T.K., Emr, S.D. J. Cell Biol. (2000) [Pubmed]
  6. Primary structure and biochemical characterization of yeast GTPase-activating proteins with substrate preference for the transport GTPase Ypt7p. Vollmer, P., Will, E., Scheglmann, D., Strom, M., Gallwitz, D. Eur. J. Biochem. (1999) [Pubmed]
  7. Regulated vacuole fusion and fission in Schizosaccharomyces pombe: an osmotic response dependent on MAP kinases. Bone, N., Millar, J.B., Toda, T., Armstrong, J. Curr. Biol. (1998) [Pubmed]
  8. Involvement of Ypt7p, a small GTPase, in traffic from late endosome to the vacuole in yeast. Schimmöller, F., Riezman, H. J. Cell. Sci. (1993) [Pubmed]
  9. Molecular cloning and functional characterization of avaB, a gene encoding Vam6p/Vps39p-like protein in Aspergillus nidulans. Oka, M., Maruyama, J., Arioka, M., Nakajima, H., Kitamoto, K. FEMS Microbiol. Lett. (2004) [Pubmed]
  10. Characterization of end4+, a gene required for endocytosis in Schizosaccharomyces pombe. Iwaki, T., Tanaka, N., Takagi, H., Giga-Hama, Y., Takegawa, K. Yeast (2004) [Pubmed]
  11. Phosphoinositide signaling and turnover: PtdIns(3)P, a regulator of membrane traffic, is transported to the vacuole and degraded by a process that requires lumenal vacuolar hydrolase activities. Wurmser, A.E., Emr, S.D. EMBO J. (1998) [Pubmed]
  12. Structure-function analysis of small G proteins from Volvox and Chlamydomonas by complementation of Saccharomyces cerevisiae YPT/SEC mutations. Fabry, S., Steigerwald, R., Bernklau, C., Dietmaier, W., Schmitt, R. Mol. Gen. Genet. (1995) [Pubmed]
  13. The major role of the Rab Ypt7p in vacuole fusion is supporting HOPS membrane association. Hickey, C.M., Stroupe, C., Wickner, W. J. Biol. Chem. (2009) [Pubmed]
  14. The Ccz1 protein interacts with Ypt7 GTPase during fusion of multiple transport intermediates with the vacuole in S. cerevisiae. Kucharczyk, R., Kierzek, A.M., Slonimski, P.P., Rytka, J. J. Cell. Sci. (2001) [Pubmed]
  15. A new role for a SNARE protein as a regulator of the Ypt7/Rab-dependent stage of docking. Ungermann, C., Price, A., Wickner, W. Proc. Natl. Acad. Sci. U.S.A. (2000) [Pubmed]
  16. Longin-like folds identified in CHiPS and DUF254 proteins: Vesicle trafficking complexes conserved in eukaryotic evolution. Kinch, L.N., Grishin, N.V. Protein Sci. (2006) [Pubmed]
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