CHM : CHM Rab escort protein
Description
The CHM (CHM Rab escort protein) is a protein-coding gene located on chromosome X.
The CHM gene provides instructions for producing the Rab escort protein-1 (REP-1), which is active (expressed) throughout the body. As an escort protein, REP-1 attaches (binds) to one of a number of Rab proteins. Following a chemical modification, REP-1 then directs the Rab protein to the membrane of one of the cell's compartments (organelles). While attached to the membrane, the Rab protein plays a role in directing the movement of proteins and organelles within cells (intracellular trafficking). After the Rab protein has reached its destination, it is released by REP-1 which then attaches to another Rab protein to begin the process again.
The CHM protein acts as a crucial component in the Rab geranylgeranyltransferase (GGTase) complex. It binds to unprenylated Rab proteins, effectively acting as a chaperone that guides these proteins to the catalytic portion of the GGTase complex, known as component B. This component, formed by RABGGTA and RABGGTB, is responsible for attaching geranylgeranyl groups to Rab proteins. Importantly, CHM remains bound to the Rab protein even after this modification. It's believed that CHM then releases the prenylated Rab protein back to the donor membrane, effectively recycling itself for subsequent rounds of Rab protein modification. Additionally, CHM can form a complex with the GGTase dimer prior to Rab protein binding. This pre-formed complex can then bind and prenylate Rab proteins, representing a potentially dominant pathway in the process of Rab protein geranylgeranylation.
CHM is also known as DXS540, GGTA, HSD-32, REP-1, TCD.
