AUTOACYLATION OF G-PROTEIN ALPHA-SUBUNITS

The palmitoylation or S-acylation of at least some G protein cu subuni ts is a dynamic process that is regulated in vivo by the activation of associated receptors. Highly purified, myristoylated G(i alpha 1) and other G protein alpha subunits react spontaneously with palmitoyl-CoA in vitro to form thioesterified proteins. This reaction requires nati ve G(i alpha 1) and occurs exclusively at Cys(3), the same residue tha t is palmitoylated in vivo. The reaction proceeds to completion, and i ts rate is roughly equal to the rate of loss of palmitate observed in pulse-chase experiments in vivo. The rate of autoacylation is signific antly enhanced by the G protein py subunit complex. Autoacylation may play a role in the dynamic thioesterification of some cellular protein s.