THE FUNCTION OF ACYL-COA-BINDING PROTEIN (ACBP) DIAZEPAM BINDING INHIBITOR (DBI)/

Acyl-CoA-binding protein has been isolated independently by five diffe rent groups based on its ability to (1) displace diazepam from the GAB A(A) receptor, (2) affect cell growth, (3) induce medium-chain acyl-Co A-ester synthesis, (4) stimulate steroid hormone synthesis, and (5) af fect glucose-induced insulin secretion. In this survey evidence is pre sented to show that ACBP is able to act as an intracellular acyl-CoA t ransporter and acyl-CoA pool former. The rat ACBP genomic gene consist s of 4 exons and is actively expressed in all tissues tested with high est concentration being found in liver. ACBP consists of 86 amino acid residues and contains 4 alpha-helices which are folded into a boomera ng type of structure with alpha-helices 1, 2 and 4 in the one arm and alpha-helix 3 and an open loop in the other arm of the boomerang. ACBP is able to stimulate mitochondrial acyl-CoA synthetase by removing ac yl-CoA esters from the enzyme. ACBP is also able to desorb acyl-CoA es ters from immobilized membranes and transport and deliver these for mi tochondrial beta-oxidation. ACBP efficiently protects acetyl-CoA carbo xylase and the mitochondrial ADP/ATP translocase against acyl-CoA inhi bition. Finally, ACBP is shown to be able to act as an intracellular a cyl-CoA pool former by overexpression in yeast. The possible role of A CBP in lipid metabolism is discussed.