The modification of peptidyl-cysteine to form peptidyl-S-geranylgeranylcysteine; formation of S-geranylgeranyl-L-cysteine may be coupled with subsequent cleavage of a carboxy-terminal tripeptide for the CAAX motif and methyl esterification of the geranylgeranylated cysteine; methyl esterification but not cleavage occurs for the CXC motif. For the type II geranylgeranyltransferase the residue may be found at the first and final positions in the sequence motif C-X-C* or at the final position in the sequence motif C-C*. These motifs are necessary but not sufficient for modification.