Thermodynamics of ligand binding to acyl-coenzyme A binding protein studied by titration calorimetry

Biochemistry. 1996 Nov 12;35(45):14118-26. doi: 10.1021/bi960545z.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acyl Coenzyme A / chemistry*
  • Animals
  • Calorimetry
  • Carrier Proteins / chemistry*
  • Cattle
  • Diazepam Binding Inhibitor
  • Entropy
  • Hydrogen-Ion Concentration
  • Ligands
  • Osmolar Concentration
  • Protein Binding
  • Recombinant Proteins
  • Solubility
  • Structure-Activity Relationship
  • Surface Properties
  • Temperature
  • Thermodynamics

Substances

  • Acyl Coenzyme A
  • Carrier Proteins
  • Diazepam Binding Inhibitor
  • Ligands
  • Recombinant Proteins