A series of specific posttranslational modifications to the CAAX box region of CAAX box proteins. CAAX box proteins are eukaryotic proteins that contain a CAAX motif where the C is a cysteine, the two A residues are aliphatic amino acids and the X can be one of several amino acids. The CAAX-box proteins undergo three sequential, enzymatic, post-translational modifications essential to their targeting: First, the proteins are prenylated by one of two prenyltransferases called farnesyltransferase and geranylgeranyltransferase-I. Prenylation results in the covalent attachment of either farnesyl or geranylgeranyl isoprenoid groups to the cysteine in the CAAX box motif. Prenylation is followed by proteolytic removal of the last three amino acids of the protein (AAX). Finally, the newly exposed carboxylate group of the isoprenylcysteine is methylated by an ER-associated prenyl-dependent carboxylmethyltransferase.
CAAX-box protein processing