Backlund P S, Simonds W F, Spiegel A M
Laboratory of General and Comparative Biochemistry, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892.
J Biol Chem. 1990 Sep 15;265(26):15572-6.
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.
对鸟嘌呤核苷酸结合蛋白（G蛋白）γ亚基的酶促甲基化在脑膜中进行了研究。使用[³H-甲基]S-腺苷甲硫氨酸在体外对脑膜进行甲基化，并且使用抗β抗体纯化G蛋白βγ复合物，以便在纯化过程中检测该蛋白。发现分离出的G蛋白βγ复合物在γ亚基上发生了羧基甲基化。通过胰蛋白酶消化将甲基定位到该蛋白的羧基末端。甲基化的胰蛋白酶肽含有一个修饰的半胱氨酸，并且非常疏水，表明存在脂酰化的额外修饰。证据表明，G-γ的羧基末端的修饰方式类似于ras蛋白所发生的加工过程。
