Myristoylation exerts direct and allosteric effects on G? conformation and dynamics in solution.

ABSTRACT: Coupling of heterotrimeric G proteins to activated G protein-coupled receptors results in nucleotide exchange on the G? subunit, which in turn decreases its affinity for both G?? and activated receptors. N-Terminal myristoylation of G? subunits aids in membrane localization of inactive G proteins. Despite the presence of the covalently attached myristoyl group, G? proteins are highly soluble after GTP binding. This study investigated factors facilitating the solubility of the activated, myristoylated protein. In doing so, we also identified myristoylation-dependent differences in regions of G? known to play important roles in interactions with receptors, effectors, and nucleotide binding. Amide hydrogen-deuterium exchange and site-directed fluorescence of activated proteins revealed a solvent-protected amino terminus that was enhanced by myristoylation. Furthermore, fluorescence quenching confirmed that the myristoylated amino terminus is in proximity to the Switch II region in the activated protein. Myristoylation also stabilized the interaction between the guanine ring and the base of the ?5 helix that contacts the bound nucleotide. The allosteric effects of myristoylation on protein structure, function, and localization indicate that the myristoylated amino terminus of G?(i) functions as a myristoyl switch, with implications for myristoylation in the stabilization of nucleotide binding and in the spatial regulation of G protein signaling.

SUBMITTER: Preininger AM 

PROVIDER: S-EPMC3312377 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature