This gene encodes component A of the RAB geranylgeranyl transferase holoenzyme. In the dimeric holoenzyme, this subunit binds unprenylated Rab GTPases and then presents them to the catalytic Rab GGTase subunit for the geranylgeranyl transfer reaction. Rab GTPases need to be geranylgeranyled on either one or two cysteine residues in their SLCterminus to localize to the correct intracellular membrane. Mutations in this gene are a cause of choroideremia; also known as tapetochoroidal dystrophy (TCD). This X-linked disease is characterized by progressive dystrophy of the choroid, retinal pigment epithelium and retina. Alternative splicing results in multiple transcript variants encoding different isoforms.[provided by RefSeq, Feb 2009]
Function:
Binds unprenylated Rab proteins, presents it to the catalytic Rab GGTase dimer, and remains bound to it after the geranylgeranyl transfer reaction. The component A is thought to be regenerated by transferring its prenylated Rab back to the donor membrane. Also a pre-formed complex consisting of CHM and the Rab GGTase dimer (RGGT or component B) can bind to and prenylate Rab proteins; this alternative pathway is proposed to be the predominant pathway for Rab protein geranylgeranylation.
Subcellular Location:
Belongs to the Rab GDI family.
DISEASE:
Defects in CHM are the cause of choroideremia (CHM) [MIM:30620]. An X-linked recessive disease characterized by a slowly progressive degeneration of the choroid, photoreceptors, and retinal pigment epithelium. Affected males develop night blindness in their teenage years followed by loss of peripheral vision and complete blindness at middle age. Carrier females are generally asymptomatic but funduscopic examination often shows patchy areas of chorioretinal atrophy.
SWISS:
P24386
Gene ID:
1121
Database links:
Entrez Gene: 1121 Human
Entrez Gene: 12662 Mouse
Omim: 300390 Human
SwissProt: P24386 Human
SwissProt: Q9QXG2 Mouse
Unigene: 496449 Human
Unigene: 257316 Mouse
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