NCIt synonyms : Geranylgeranyltransferase Type I; GGTase-I;
NCIt definition : Alpha-beta heterodimeric human GGTase-I transfers a geranylgeranyl moiety to the Cys
of a C-terminal CAAX motif in candidate proteins as a means of membrane localization.
The conserved 48-kDa alpha subunit of GGTase-I is identical to the alpha subunit (FNTA)
of Farnesyl Protein Transferase. The conserved 42-kDa Protein Geranylgeranyltransferase
Type I Beta Subunit (PGGT1B Gene), containing 4 PFTB repeats, is distinct from the
beta subunit (FNTB) of Farnesyl Protein Transferase; FNTB and PGGT1B are catalytic
for specific substrates. The mammalian counterpart of CDC43 (S. cerevisiae) and responsible
for peptide binding, PGGT1B acts on Rac1, Rac2, Rap1A, and Rap1B. Interacting with
TGF-beta and Activin Type I receptors, FNTA is likely a key component of p21ras signaling,
a farnesyltransferase substrate. (NCI);