VPS21 encodes a rab5-like GTP binding protein that is required for the sorting of yeast vacuolar proteins

EMBO J. 1994 Mar 15;13(6):1297-309.


Many of the vacuolar protein sorting (vps) mutants of Saccharomyces cerevisiae exhibit severe defects in the sorting of vacuolar proteins but still retain near-normal vacuole morphology. The gene affected in one such mutant, vps21, has been cloned and found to encode a member of the ras-like GTP binding protein family. Sequence comparisons with other known GTP binding proteins indicate that Vps21p is unique but shares striking similarity with mammalian rab5 proteins (> 50% identity and > 70% similarity). Regions with highest similarity are clustered within the putative GTP binding motifs and the proposed effector domains of the Vps21/rab5 proteins. Point mutations constructed within these conserved regions inactivate Vps21p function; the mutant cells missort and secrete the soluble vacuolar hydrolase carboxypeptidase Y (CPY). Cells carrying a complete deletion of the VPS21 coding sequence (i) are viable but exhibit a growth defect at 38 degrees C, (ii) missort multiple vacuolar proteins, (iii) accumulate 40-50 nm vesicles and (iv) contain a large vacuole. VPS21 encodes a 22 kDa protein that binds GTP and fractionates with subcellular membranes. Mutant analysis indicates that the association with a membrane(s) is dependent on geranylgeranylation of the C-terminal cysteine residue(s) of Vps21p. We propose that Vps21p functions in the targeting and/or fusion of transport vesicles that mediate the delivery of proteins to the vacuole.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Biological Transport
  • Fungal Proteins / metabolism*
  • GTP-Binding Proteins / genetics*
  • GTP-Binding Proteins / metabolism
  • Mating Factor
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Molecular Sequence Data
  • Peptides / metabolism
  • Point Mutation
  • Restriction Mapping
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Sequence Homology, Amino Acid
  • Vacuoles / metabolism
  • rab GTP-Binding Proteins*
  • rab5 GTP-Binding Proteins


  • Fungal Proteins
  • Membrane Proteins
  • Peptides
  • Mating Factor
  • GTP-Binding Proteins
  • rab GTP-Binding Proteins
  • rab5 GTP-Binding Proteins

Associated data

  • GENBANK/Z29338