CHEMICAL INHIBITION OF MYRISTOYLATION OF THE G-PROTEIN G(I1)ALPHA BY 2-HYDROXYMYRISTATE DOES NOT INTERFERE WITH ITS PALMITOYLATION OR MEMBRANE ASSOCIATION - EVIDENCE THAT PALMITOYLATION, BUT NOT MYRISTOYLATION, REGULATES MEMBRANE ATTACHMENT

The alpha-subunit of the G-protein G(il)alpha is normally dually acyla ted at its N-terminus with the saturated fatty acids myristate and pal mitate, Inhibition of protein myristoylation by treatment with 2-hydro xymyristate prevented neither the incorporation of [H-3]palmitate nor the membrane association of this protein when expressed in COS cells. Construction of a mutant of G(il)alpha in which serine-6 was replaced by aspartic acid prevented both myristoylation and palmitoylation, and the expressed protein was found primarily in the cytoplasmic fraction . These data indicate that myristoylation is not an absolute requireme nt for palmitoylation of G(il)alpha and that palmitoylation, but not m yristoylation, plays a key role in membrane association of this G-prot ein alpha-subunit.