The binding of the fluorescent ATP analogue 2′(3′)-trinitrophenyladenosine-5′-triphosphate to rat liver fatty acid-binding protein

Abstract

The less polar fluorescent analogue of ATP, 2′(3′)-trinitrophenyl-5′-triphosphate bound to rat liver fatty acid-binding protein with high affinity ( K d 6.3 × 10 −6 M) and 1:1 molar stoichiometry. This probe bound to the fatty acid binding site of the protein and was displaced by oleic acid and oleoyl CoA. High concentrations of ATP did not cause significant displacement of the fluorescent ATP analogue. Since the anionic part of this molecule is the triphosphate group it is difficult to envisage this group being accommodated at an anion binding site within the non-polar core of this protein as is the case with other fatty acid binding proteins. Therefore it is anticipated that the ligand must bind to liver fatty acid-binding protein with these triphosphate group surface exposed. Caution must be exercised when using the more hydrophobic fluorescent analogue of ATP to investigate the ATP binding properties of proteins.