Thermodynamics of ligand binding to acyl-coenzyme A binding protein studied by titration calorimetry.
Ligand binding to recombinant bovine acyl-CoA binding protein (ACBP) was examined using isothermal microcalorimetry. Microcalorimetric measurements confirm that the binding affinity of acyl-CoA esters for ACBP is strongly dependent on the length of the acyl chain with a clear preference for acyl-CoA esters containing more than eight carbon atoms and that the 3'-phosphate of the ribose accounts for almost half of the binding energy. Binding of acyl-CoA esters, with increasing chain length, to ACBP was clearly enthalpically driven with a slightly unfavorable entropic contribution. Accessible surface areas derived from the measured enthalpies were compared to those calculated from sets of three-dimensional solution structures and showed reasonable correlation, confirming the enthalphically driven binding. Binding of dodecanoyl-CoA to ACBP was studied at various temperatures and was characterized by a weak temperature dependence on delta G zero and a strong enthalpy-entropy compensation. This was a direct consequence of a large heat capacity delta Cp caused by the presence of strong hydrophobic interactions. Furthermore, the binding of dodecanoyl-CoA was studied at various pH values and ionic strengths. The data presented here state that ACBP binds long-chain acyl-CoA esters with very high affinity and suggest that ACBP acts as a housekeeping protein with no pronounced built-in specificity.
Institute of Biochemistry, Odense University, Denmark.
N J
NJ
Faergeman
B W
BW
Sigurskjold
B B
BB
Kragelund
K V
KV
Andersen
J
J
Knudsen
D000214:Acyl Coenzyme A / Q000737:chemistry*; D000818:Animals; D002151:Calorimetry; D002352:Carrier Proteins / Q000737:chemistry*; D002417:Cattle; D026261:Diazepam Binding Inhibitor; D019277:Entropy; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D009994:Osmolar Concentration; D011485:Protein Binding; D011994:Recombinant Proteins; D012995:Solubility; D013329:Structure-Activity Relationship; D013499:Surface Properties; D013696:Temperature; D013816:Thermodynamics
D000214:Acyl Coenzyme A; D002352:Carrier Proteins; D026261:Diazepam Binding Inhibitor; D008024:Ligands; D011994:Recombinant Proteins