Two GTPase isoforms, Ypt31p and Ypt32p, are essential for Golgi function in yeast

EMBO J. 1996 Dec 2;15(23):6460-75.


In eukaryotic cells, monomeric GTPases of the Ypt/Rab family function as regulators at defined steps of vesicular transport in exo- and endocytosis. Here we report on the isolation and characterization of two genes (YPT31 and YPT32) of the yeast Saccharomyces cerevisiae which encode members of the Ypt family exhibiting >80% sequence identity. Whereas the disruption of one of the two genes was phenotypically neutral, the disruption of both YPT31 and YPT32 led to lethality. Depletion of wild-type Ypt31p or of a short-lived ubiquitin-Ypt31p in a ypt32 null background led to a massive accumulation of Golgi-like membranes, an inhibition of invertase secretion and defects in vacuolar protein maturation. Similar alterations were observed in a conditional-lethal ypt31-1 mutant at 30 min after shift to the non-permissive temperature. According to subcellular fractionation, a significant part of Ypt31p appeared to be located in Golgi-enriched membrane fractions. In accordance with this, indirect immunofluorescence using affinity-purified anti-Ypt31p antibodies gave a punctate staining similar to that observed with Golgi-located proteins. From the phenotypic alterations observed in ypt31 and ypt32 mutants, it seems likely that the two GTPases are involved in intra-Golgi transport or in the formation of transport vesicles at the most distal Golgi compartment.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Dogs
  • GTP Phosphohydrolases / chemistry*
  • GTP Phosphohydrolases / genetics
  • GTP Phosphohydrolases / metabolism*
  • Genes, Fungal
  • Glycoside Hydrolases / metabolism
  • Golgi Apparatus / physiology*
  • Golgi Apparatus / ultrastructure
  • Isoenzymes / chemistry
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Kinetics
  • Microscopy, Electron
  • Molecular Sequence Data
  • Multigene Family
  • Mutagenesis
  • Polymerase Chain Reaction
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Restriction Mapping
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / ultrastructure
  • Sequence Homology, Amino Acid
  • beta-Fructofuranosidase


  • Isoenzymes
  • Recombinant Proteins
  • Glycoside Hydrolases
  • beta-Fructofuranosidase
  • GTP Phosphohydrolases

Associated data

  • GENBANK/X72833
  • GENBANK/X72834