Lipid modification of G proteins.

The heterotrimeric guanine nucleotide-binding G proteins, composed of α, β, and γ subunits, act as signal transducers between cell surface receptors and downstream effector molecules, leading to changes in intracellular second messengers. The superfamily of ras-related low-molecular-mass GTP-binding G proteins is involved in a number of cellular functions, including cell differentiation and growth control, actin polymerization and cytoskeleton arrangement, and intracellular vesicular transport. The heterotrimeric G proteins and the ras-related low-molecular-mass G proteins are modified in vivo by a number of lipid groups, including palmitate, myristate, heterogeneous fatty-acyl groups (C12:0, C14:1, or C14:2 fatty-acyl groups), and C15 farnesyl or C20 geranylgeranyl isoprenoids. Lipid modification of G proteins increases the hydrophobicity of the proteins. In this review, we describe the various types of lipid modification of G proteins and discuss the significance of lipid modification with respect to G-protein function.