Geranylgeranylation is a form of
prenylation, which is a
post-translational modification
In molecular biology, post-translational modification (PTM) is the covalent process of changing proteins following protein biosynthesis. PTMs may involve enzymes or occur spontaneously. Proteins are created by ribosomes, which translation (biolog ...
of proteins that involves the attachment of one or two 20-carbon lipophilic geranylgeranyl
isoprenoid units from
geranylgeranyl diphosphate to one or two
cysteine
Cysteine (; symbol Cys or C) is a semiessential proteinogenic amino acid with the chemical formula, formula . The thiol side chain in cysteine enables the formation of Disulfide, disulfide bonds, and often participates in enzymatic reactions as ...
residue(s) at the
C-terminus
The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, carboxy tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain (protein
Proteins are large biomolecules and macromolecules that comp ...
of specific proteins. Prenylation (including geranylgeranylation) is thought to function, at least in part, as a membrane anchor for proteins.
The process of geranylgeranylation can be catalyzed by either
geranylgeranyl transferase I (GGTase I) or
Rab GGTase (also GGTase II). GGTase I catalyzes the addition of one geranylgeranyl group onto the C-terminal consensus sequence CAAL (somewhat similar to farnesyltransferase reactions), where C=cysteine, A=any aliphatic amino acid, and L=leucine. Rab GGTase adds a total of two geranylgeranyl groups onto two cysteine residues at the C-terminal consensus sequence CXC or XXCC. The source of the geranylgeranyl group is geranylgeranyl diphosphate, which is synthesized by
GGPS1 within the
isoprenoid biosynthetic pathway.
An example of this can be seen in the
lipid anchoring of the
Rho GTPase family of
signaling molecule
In biology, cell signaling (cell signalling in British English) is the Biological process, process by which a Cell (biology), cell interacts with itself, other cells, and the environment. Cell signaling is a fundamental property of all Cell (biol ...
s and the gamma subunit of
heterotrimeric G proteins.
References
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Proteins
Gene expression
Molecular biology