cDNA cloning of component A of Rab geranylgeranyl transferase and demonstration of its role as a Rab escort protein.
cDNA cloning of component A of rat Rab geranylgeranyl transferase confirms identity of the protein with the human choroideremia gene product and its resemblance to Rab3A guanine nucleotide dissociation inhibitor (GDI), which binds prenylated Rabs. In biochemical assays we demonstrate that component A binds unprenylated Rab1A, presents it to the catalytic component B, and remains bound to it after the geranylgeranyl transfer reaction. In the absence of detergents, the reaction terminates when all of component A is occupied with prenylated Rab. Detergents allow multiple rounds of catalysis, apparently by dissociating the component A-Rab complex and thus allowing recycling of component A. Within the cell, component A may be regenerated by transferring its prenylated Rab to a protein acceptor, such as Rab3A GDI. In view of its function in escorting Rab proteins during and presumably after the prenyl transfer reaction, we propose to rename component A as Rab escort protein (REP). A genetic defect in REP underlies human choroideremia, a disease of retinal degeneration.
Andres
D A
DA
Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas 75235.
Seabra
M C
MC
Brown
M S
MS
Armstrong
S A
SA
Smeland
T E
TE
Cremers
F P
FP
Goldstein
J L
JL
D048868:Adaptor Proteins, Signal Transducing; D019883:Alkyl and Aryl Transferases; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics*; D002417:Cattle; D002478:Cells, Cultured; D003001:Cloning, Molecular; D019204:GTP-Binding Proteins / Q000235:genetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D017368:Protein Prenylation; D051381:Rats; D017386:Sequence Homology, Amino Acid; D014166:Transferases / Q000235:genetics*; D020691:rab GTP-Binding Proteins; D020761:rab1 GTP-Binding Proteins
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C513166:Chm protein, rat; D014166:Transferases; D019883:Alkyl and Aryl Transferases; C075607:Rab geranylgeranyltransferase; D019204:GTP-Binding Proteins; D020691:rab GTP-Binding Proteins; D020761:rab1 GTP-Binding Proteins