Crystal structure of a bacterial homologue of the bile acid sodium symporter ASBT

Elevated cholesterol levels significantly increase the risk of atherosclerosis and cardiovascular diseases. Cholesterol is eliminated from the body following conversion to bile acids, so the apical sodium-dependent bile acid transporter (ASBT) that reabsorbs bile acid in the intestine is a major drug target for cholesterol-lowering therapy. The X-ray crystal structure of a bacterial homologue of ASBT bound to its bile acid substrate has now been determined. The substrate (taurocholate) is found in a large hydrophobic cavity between the protein's 'core' and 'panel' domains, suggesting a possible transport mechanism for this important biomolecule.