The α‐subunits of G‐proteins G12 and G13 are palmitoylated, but not amidically myristoylated

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Abstract
The α‐subunits of the G‐proteins G12 and G13, were expressed with a baculovirus system in insect cells and analysed for acylation. Both proteins incorporated tritiated palmitic and to a lesser extent also tritiated myristic acid. Radiolabel from both fatty acids was sensitive to treatment with neutral hydroxylamine. This result supports a thioester‐type fatty acid bond and argues against amidical N‐myristoylation. Fatty acid analysis after labeling with [3H]palmitic acid showed that palmitate represents the predominant fatty acid linked to Gα12 and Gα13. Separation of cells into cytosolic and membranous fractions revealed that palmitoylated α‐subunits of G12 were exclusively membrane‐bound, whereas [35S]methionine‐labeled proteins were detected in soluble and particulate fractions. Inhibition of protein synthesis with cycloheximide did not block palmitoylation of the α‐subunits. which indicates that palmitoylation occurs independently of protein synthesis.