title: Carboxyl methylation and COOH-terminal processing of the brain G-protein gamma-subunit.
abstract: The enzymatic methylation of the guanine nucleotide-binding proteins (G-proteins) gamma-subunit was investigated in brain membranes. Brain membranes were methylated in vitro using [3H-methyl]S-adenosylmethionine, and the G-protein beta gamma-complex was purified using an anti-beta antibody to assay for the protein during purification. The isolated G-protein beta gamma-complex was found to be carboxyl methylated on the gamma-subunit. The methyl group was localized by tryptic digestion to the carboxyl-terminal of the protein. The methylated tryptic peptides contained a modified cysteine and were very hydrophobic, suggesting additional modification by lipidation. The evidence suggests that the COOH-terminal of G-gamma is modified in a manner similar to the processing that occurs with the ras proteins.
authors.affiliation: Laboratory of General and Comparative Biochemistry, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: P S
authors.initials: PS
authors.lastname: Backlund
authors.forename: W F
authors.initials: WF
authors.lastname: Simonds
authors.forename: A M
authors.initials: AM
authors.lastname: Spiegel
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000302:isolation & purification; D046911:Macromolecular Substances; D008745:Methylation; D008970:Molecular Weight; D010449:Peptide Mapping; D011499:Protein Processing, Post-Translational; D011817:Rabbits; D014357:Trypsin
chemical_list: D000596:Amino Acids; D046911:Macromolecular Substances; D014357:Trypsin; D019204:GTP-Binding Proteins