Posttranslational Modification of the Ha-ras Oncogene Protein: Evidence for a Third Class of Protein Carboxyl Methyltransferases

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 85; no. 13; pp. 4643 - 4647
• Main Authors: Clarke, Steven, Vogel, Joseph P., Deschenes, Robert J., Stock, Jeffry
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01.07.1988; National Acad Sciences
• Subjects: 550201 - Biochemistry- Tracer Techniques; AMINO ACIDS; ANIMAL CELLS; ANIMALS; BASIC BIOLOGICAL SCIENCES; BETA DECAY RADIOISOTOPES; BETA-MINUS DECAY RADIOISOTOPES; BIOCHEMISTRY; Biological and medical sciences; CARBOXYLIC ACIDS; Cell lines; Cell physiology; Cell transformation and carcinogenesis. Action of oncogenes and antioncogenes; Cell Transformation, Neoplastic; CHEMICAL REACTIONS; CHEMISTRY; CONNECTIVE TISSUE CELLS; CYSTEINE; DAYS LIVING RADIOISOTOPES; DRUGS; ELECTROPHORESIS; EMBRYONIC CELLS; Embryos; ENZYMES; Esters; EVEN-ODD NUCLEI; FIBROBLASTS; Fibroblasts - metabolism; Fundamental and applied biological sciences. Psychology; Gels; GENES; HYDROGEN COMPOUNDS; ISOTOPES; LIGHT NUCLEI; LIPOTROPIC FACTORS; MAMMALS; METHIONINE; METHYL TRANSFERASES; METHYLATION; Molecular and cellular biology; Neoplasm Proteins - biosynthesis; NUCLEI; ONCOGENES; ORGANIC ACIDS; ORGANIC COMPOUNDS; ORGANIC SULFUR COMPOUNDS; Phosphoproteins; POST-TRANSLATION MODIFICATION; Protein Methyltransferases - metabolism; Protein Processing, Post-Translational; PROTEINS; Proto-Oncogene Proteins - biosynthesis; Proto-Oncogene Proteins p21(ras); Radioactive decay; RADIOISOTOPES; RATS; RODENTS; S-Adenosylmethionine - metabolism; Sodium; SOMATIC CELLS; SULFUR 35; SULFUR ISOTOPES; THIOLS; TRANSFERASES; TRITIUM COMPOUNDS; Tumor Suppressor Protein p53; VERTEBRATES; Posttranslational modification; Proteins; Gene expression; Cell transformation; C-Onc gene; Malignant transformation
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.85.13.4643

The ras oncogene products require membrane localization for their function, and this is thought to be accomplished by the addition of a palmitoyl group to a cysteine residue near the carboxyl terminus of the nascent chain. A lipidated carboxyl-terminal cysteine residue is also found in sequence-related yeast sex factors, and in at least two cases, the α -carboxyl group is also methyl esterified. To determine if ras proteins are themselves modified by a similar type of methylation reaction, we incubated rat embryo fibroblasts transformed with p53 and activated Ha-ras oncogenes with L-[methyl-3H]methionine under conditions in which the isotope was converted to the methyl donor S-adenosyl-L-[methyl-3H]methionine. By using an assay that detects methyl ester linkages, we found that immunoprecipitated ras proteins are in fact esterified and that the stability of these esters is consistent with a carboxyl-terminal localization. This methylation reaction may be important in regulating the interaction of ras proteins with plasma membrane components. The presence of analogous carboxyl-terminal tetrapeptide sequences in other proteins may provide a general recognition sequence for lipidation and methylation modification reactions.