Agonist-Mediated Turnover of G-Protein α-Subunit Palmitoyl Groups
Membrane associated proteins are classically thought of as proteins that are inserted into the membrane lipid bilayer by virtue of transmembrane-spanning regions. Although heterotrimeric G proteins are membrane-associated, they do not contain such transmembrane regions, but have been shown by recent work to be located at the inner surface of the plasma membrane by virtue of lipid modifications (1). One of these lipid modifications, myristoylation, is an irreversible cotranslational lipid modification that involves the addition of a saturated 14 carbon acyl group at the NH2-terminal glycine of a subset of heterotrimeric G-protein α-subunits. A second modification, palmitoylation, in comparison, is a dynamic, reversible posttranslational modification in which the addition of a 16 carbon saturated fatty acyl group occurs via a labile thioester bond on cysteine residues. This modification is present on all heterotrimeric G-protein α-subunits examined to date, with the exception of transducin (which is myristoylated and further modified by other less hydrophobic fatty acids).
KeywordsPalmitic Acid Membrane Lipid Bilayer Dialysis Tubing Newborn Calf Serum Lipid Modification
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