Digeranylgeranylation

Digeranylgeranylation is a post-translational modification that occurs in some proteins. It involves the covalent attachment of two geranylgeranyl pyrophosphate (GGPP) molecules to specific cysteine residues within the protein. This process is catalyzed by a group of enzymes known as protein geranylgeranyltransferases (PGGTs). Unlike prenylation reactions that add a single isoprenoid group, digeranylgeranylation adds two such groups. The geranylgeranyl group is a 20-carbon isoprenoid unit.

The digeranylgeranylation of proteins plays a role in protein localization, membrane association, and protein-protein interactions. Proteins that undergo this modification are often found associated with cellular membranes, which can be crucial for their function. The added hydrophobic geranylgeranyl chains can facilitate insertion into lipid bilayers or interaction with other hydrophobic domains.

This modification is distinct from other prenylation modifications like farnesylation and geranylgeranylation, which involve the addition of 15-carbon and 20-carbon isoprenoid chains, respectively, but typically only one per protein. The specific enzymes and the consensus sequences within the target proteins dictate whether digeranylgeranylation or other prenylation events occur. Research into digeranylgeranylation is ongoing, aiming to fully elucidate its biological significance and the full range of proteins that undergo this modification.