Rab proteins geranylgeranyltransferase component A 2 (CHML)

Substrate-binding subunit (component A) of the Rab geranylgeranyltransferase (GGTase) complex. Binds unprenylated Rab proteins and presents the substrate peptide into the catalytic component B.

The component A is thought to be regenerated by moving its prenylated Rab back into the donor membrane. Less powerful than CHM in encouraging prenylation of Rab3 family.