Anti-CHM Antibody Picoband® Fluoro488 Conjugated

Rab escort protein 1 (REP1) also known as rab proteins geranylgeranyltransferase component A 1 is an enzyme that in humans is encoded by the CHM gene. It is mapped to Xq21.2. 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 C-terminus 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. Alternatively spliced transcript variants have been found for this gene.

A synthetic peptide corresponding to a sequence at the N-terminus of human CHM, which shares 88.9% amino acid (aa) sequence identity with both mouse and rat CHM.

Expressed in monocytes and mature macrophages such as Kupffer cells in the liver, red pulp macrophages in the spleen, cortical macrophages in the thymus, resident bone marrow macrophages and meningeal macrophages of the central nervous system. Expressed also in blood. Isoform 1 is the lowest abundant in the blood. Isoform 2 is the lowest abundant in the liver and the spleen. Isoform 3 is the predominant isoform detected in the blood.

Substrate-binding subunit of the Rab geranylgeranyltransferase (GGTase) complex. Binds unprenylated Rab proteins and presents the substrate peptide to the catalytic component B composed of RABGGTA and RABGGTB, 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. Besides, 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.

1. Entrez Gene: CHM choroideremia (Rab escort protein 1) . 2. Molloy CM, van de Pol TJ, Brohet RM, Ropers HH, Cremers FP (May 1992) . Three RFLPs for pZ11 (DXS540) in the choroideremia gene at Xq21.2. Nucleic Acids Res. 20 (6) : 1434.