Acyl-CoA-binding protein
In molecular biology, the Acyl-CoA-binding protein is a small protein that binds medium- and long-chain acyl-CoA esters with very high affinity and may function as an intracellular carrier of acyl-CoA esters. ACBP is also known as diazepam binding inhibitor or endozepine because of its ability to displace diazepam from the benzodiazepine recognition site located on the GABA type A receptor. It is therefore possible that this protein also acts as a neuropeptide to modulate the action of the GABA receptor.
ACBP is a highly conserved protein of about 90 amino acids that is found in all four eukaryotic kingdoms, Animalia, Plantae, Fungi and Protista, and in some eubacterial species.
Although ACBP occurs as a completely independent protein, intact ACB domains have been identified in a number of large, multifunctional proteins in a variety of eukaryotic species. These include large membrane-associated proteins with N-terminal ACB domains, multifunctional enzymes with both ACB and peroxisomal enoyl-CoA Delta, Delta-enoyl-CoA isomerase domains, and proteins with both an ACB domain and ankyrin repeats.
The ACB domain consists of four alpha-helices arranged in a bowl shape with a highly exposed acyl-CoA-binding site. The ligand is bound through specific interactions with residues on the protein, most notably several conserved positive charges that interact with the phosphate group on the adenosine-3'phosphate moiety, and the acyl chain is sandwiched between the hydrophobic surfaces of CoA and the protein.
Other proteins containing an ACB domain include:
