title: Post-translational modifications of p21rho proteins.
abstract: Post-translational modifications of the ras proteins, which are required for plasma membrane localization and biological function of the proteins, have been shown to include prenylation and carboxymethylation at the carboxyl terminal cysteine residue of the cysteine-aliphatic amino acid-aliphatic amino acid-any amino acid (CAAX) box. In addition, p21Ha-ras and p21N-ras, but not p21K-ras (B), are palmitoylated. The three mammalian rho proteins (A, B, and C) are also members of the ras superfamily but have distinct biological activities and different intracellular distributions from p21ras. Analysis showed all three rho proteins are modified by a COOH-terminal carboxymethylation similar to p21ras, whereas p21rhoC labeled with [3H]mevalonic acid in vivo revealed the presence of a C20 prenoid, similar to that already described for p21rhoA. However, in vivo and in vitro studies of p21rhoB showed this protein to be modified by both C15 and C20 prenoids. Mutation of C193 in the CAAX box abolished prenylation, whereas mutation of the adjacent C192 resulted in a significant reduction in the amount of the C20, but not C15 prenoid, recovered from p21rhoB. In vivo labeling studies with [3H]palmitic acid and mutational analysis showed that both cysteine residues at 189 and 192 upstream of the CAAX box in p21rhoB are sites for palmitoylation. We conclude that there are different populations of post-translationally modified p21rhoB in the cell and that the sequence specificity for geranylgeranyl- and farnesyltransferases may be more complicated than previously proposed.
authors.affiliation: Section of Cell and Molecular Biology, Chester Beatty Laboratories, London, United Kingdom.
authors.forename: P
authors.initials: P
authors.lastname: Adamson
authors.forename: C J
authors.initials: CJ
authors.lastname: Marshall
authors.forename: A
authors.initials: A
authors.lastname: Hall
authors.forename: P A
authors.initials: PA
authors.lastname: Tilbrook
mesh_terms: D000595:Amino Acid Sequence; D002264:Carboxylic Acids / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008745:Methylation; D008798:Mevalonic Acid / Q000737:chemistry; D008969:Molecular Sequence Data; D015689:Oncogene Protein p21(ras) / Q000235:genetics / Q000378:metabolism; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism; D017368:Protein Prenylation; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; D020743:rhoB GTP-Binding Protein
chemical_list: D002264:Carboxylic Acids; D008565:Membrane Proteins; D010169:Palmitic Acids; D011994:Recombinant Proteins; D019308:Palmitic Acid; D019204:GTP-Binding Proteins; D015689:Oncogene Protein p21(ras); D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; D020743:rhoB GTP-Binding Protein; D008798:Mevalonic Acid