Acyl-CoA-binding protein

In molecular biology, the acyl-CoA-binding protein (ACBP) is a small (10 kDa) 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.^[1] ACBP is also known as diazepam binding inhibitor (DBI) or endozepine (EP) because of its ability to displace diazepam from the benzodiazepine (BZD) 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.^[2]

ACBP
Acyl-CoA-binding protein monomer, Human
Identifiers
Symbol	ACBP
Pfam	PF00887
InterPro	IPR000582
PROSITE	PDOC00686
SCOP2	1aca / SCOPe / SUPFAM
OPM superfamily	295
OPM protein	2wh5
CDD	cd00435
Membranome	497
Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

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.^[3]

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(3), Delta(2)-enoyl-CoA isomerase domains, and proteins with both an ACB domain and ankyrin repeats.^[3]

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.^[4]

Other proteins containing an ACB domain include:

• Endozepine-like peptide (ELP) (gene DBIL5) from mouse.^[5] ELP is a testis-specific ACBP homologue that may be involved in the energy metabolism of the mature sperm.
• MA-DBI, a transmembrane protein of unknown function which has been found in mammals. MA-DBI contains a N-terminal ACB domain.
• DRS-1,^[6] a human protein of unknown function that contains a N-terminal ACB domain and a C-terminal enoyl-CoA isomerase/hydratase domain.