Rom1p and Rom2p are GDP/GTP exchange proteins (GEPs) for the Rho1p small GTP binding protein in Saccharomyces cerevisiae

EMBO J. 1996 May 1;15(9):2196-207.


The RHO1 gene encodes a homolog of the mammalian RhoA small GTP binding protein in the yeast Saccharomyces cerevisiae. Rho1p is localized at the growth site and is required for bud formation. Multicopy suppressors of a temperature-sensitive, dominant negative mutant allele of RHO1, RHO1(G22S, D125N), were isolated and named ROM (RHO1 multicopy suppressor). Rom1p and Rom2p were found to contain a DH (Dbl homologous) domain and a PH (pleckstrin homologous) domain, both of which are conserved among the GDP/GTP exchange proteins (GEPs) for the Rho family small GTP binding proteins. Disruption of ROM2 resulted in a temperature-sensitive growth phenotype, whereas disruption of both ROM1 and ROM2 resulted in lethality. The phenotypes of deltarom1deltarom2 cells were similar to those of deltarho1 cells, including growth arrest with a small bud and cell lysis. Moreover, the temperature-sensitive growth phenotype of deltarom2 was suppressed by overexpression of RHO1 or RHO2, but not of CDC42. The glutathione-S-transferase (GST) fusion protein containing the DH domain of Rom2p showed the lipid-modified Rholp-specific GDP/GTP exchange activity which was sensitive to Rho GDP dissociation inhibitor. These results indicate that Rom1p and Rom2p are GEPs that activate Rho1p in S.cerevisiae.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • DNA Primers
  • GTP-Binding Proteins / genetics
  • GTP-Binding Proteins / metabolism*
  • Genes, Suppressor
  • Guanine Nucleotide Exchange Factors
  • Molecular Sequence Data
  • Mutation
  • Phenotype
  • Proteins / metabolism*
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins
  • Sequence Homology, Amino Acid
  • Temperature
  • rho GTP-Binding Proteins*


  • DNA Primers
  • Guanine Nucleotide Exchange Factors
  • Proteins
  • Saccharomyces cerevisiae Proteins
  • GTP-Binding Proteins
  • RHO1 protein, S cerevisiae
  • rho GTP-Binding Proteins

Associated data

  • GENBANK/D83171