title: N-Myristoylation and betagamma play roles beyond anchorage in the palmitoylation of the G protein alpha(o) subunit.
abstract: Many of the alpha subunits of heterotrimeric GTP-binding regulatory proteins (G proteins) are palmitoylated, a modification proposed to play a key role in the stable anchorage of the subunits to the plasma membrane. Palmitoylation of alpha subunits from the G(i) family is preceded by N-myristoylation, which alone or together with betagamma probably supports a reversible interaction of the alpha subunit with membrane as a prerequisite to the eventual incorporation of palmitate. Previous studies have not addressed, however, the question of whether membrane association alone, carried out through N-myristoylation, interaction with betagamma, or other events, is sufficient for palmitoylation. We report here for alpha(o) that it is not. We found that N-myristoylation is required for palmitoylation at least in part because it supports events subsequent to membrane attachment. Mutants of alpha(o) designed to target the subunit to membrane without an N-myristoyl group are unable to be palmitoylated as evaluated by incorporation of [(3)H]palmitate. Mutants of alpha(o) unable to interact normally with betagamma yet still attach to membrane demonstrate that betagamma, in contrast, is not required for palmitoylation. betagamma becomes necessary, however, when the N-myristoyl group is absent. Our results suggest that N-myristoylation and betagamma, while almost certainly relevant to the reversible interaction of alpha(o) with membrane, also play at least partly overlapping, post-anchorage roles in palmitoylation.
authors.affiliation: Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6084, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: R T
authors.initials: RT
authors.lastname: Windh
authors.forename: C A
authors.initials: CA
authors.lastname: Chen
authors.forename: D R
authors.initials: DR
authors.lastname: Manning
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000818:Animals; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D019814:Myristic Acid / Q000378:metabolism*; D019308:Palmitic Acid / Q000378:metabolism*; D051381:Rats
chemical_list: D019814:Myristic Acid; D000246:Adenosine Diphosphate Ribose; D019308:Palmitic Acid; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D020962:Heterotrimeric GTP-Binding Proteins