Carboxyl methylation and COOH-terminal processing of the brain G-protein gamma-subunit

• Published in: The Journal of biological chemistry Vol. 265; no. 26; pp. 15572 - 15576
• Main Authors: P S Backlund, Jr, W F Simonds, A M Spiegel
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 15.09.1990
• Subjects: Amino Acids - analysis; Animals; Biological and medical sciences; Brain - metabolism; Chromatography, Gel; Chromatography, High Pressure Liquid; Electrophoresis, Polyacrylamide Gel; Fundamental and applied biological sciences. Psychology; GTP-Binding Proteins - genetics; GTP-Binding Proteins - isolation & purification; Macromolecular Substances; Methylation; Molecular and cellular biology; Molecular genetics; Molecular Weight; Peptide Mapping; Protein Processing, Post-Translational; Rabbits; Translation. Translation factors. Protein processing; Trypsin; Brain; GTP; Molecular processing; Radiolabelling; Gel electrophoresis; HPLC chromatography; Rabbit; Lagomorpha; In vitro; C terminal-Sequence; Binding protein; Vertebrata; Mammalia; Plasma membrane; Gel filtration; Methylation
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)55435-1

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.