A novel N-terminal motif for palmitoylation of G-protein alpha subunits.
We have examined the post-translational processing of G alpha subunits expressed endogenously in rat PC12 and NG108-15 rat/mouse hybrid cells, and after transfection of cDNA expression constructs into COS cells. Thioester-linked palmitoylation of alpha o, alpha s, alpha q/alpha 11 and alpha 12 has been detected by metabolic labelling with [3H]palmitate and immunoprecipitation. Palmitoylation of alpha o occurs post-translationally in cells treated with protein-synthesis inhibitors, suggesting possible dynamic acylation. Palmitoylation of the C-terminal CAAX motif has been excluded. Site-directed mutagenesis of alpha o has been used to implicate the site of modification as a cysteine residue next to the N-terminal myristoylated glycine, in a novel protein-lipid modification motif Met-Gly-Cys. The non-palmitoylated alpha o mutant is still myristoylated but shows reduced membrane binding, suggesting that reversible palmitoylation may regulate G alpha localization and function.
Parenti
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M
Dipartimento di Farmacología, Milan, Italy.
Viganó
M A
MA
Newman
C M
CM
Milligan
G
G
Magee
A I
AI
D000215:Acylation; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004247:DNA / Q000235:genetics; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006822:Hybrid Cells; D007163:Immunosorbent Techniques; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D019814:Myristic Acid; D009227:Myristic Acids / Q000378:metabolism; D016716:PC12 Cells; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D051381:Rats; D014162:Transfection
D009227:Myristic Acids; D010169:Palmitic Acids; D019814:Myristic Acid; D019308:Palmitic Acid; D004247:DNA; D019204:GTP-Binding Proteins