Effects of carboxyl methylation of photoreceptor G protein gamma-subunit in visual transduction.

摘要: G protein gamma-subunits are isoprenylated and carboxyl-methylated at the C-terminal cysteine, which is indispensable for function of photoreceptor transducin (T alpha beta gamma). However, physiological role methylation its reversibility have been unclear. Here we isolated methylated non-methylated forms farnesylated T gamma, demonstrated that remarkably facilitates not only membrane association gamma but also subunit interaction between gamma. Consequently, functional coupling with light-activated receptor, metarhodopsin II, was stabilized by methylation, resulting in acceleration GTP S (guanosine 5'-3-O-(thio) triphosphate) binding to alpha. An examination suggested kept fully rod outer segments. These observations indicate plays an important most efficient photon-signal transduction process cells.