Binding of warfarin influences the acid-base equilibrium of H242 in sudlow site I of human serum albumin.
Sudlow Site I of human serum albumin (HSA) is located in subdomain IIA of the protein and serves as a binding cavity for a variety of ligands. In this study, the binding of warfarin (W) is examined using computational techniques and isothermal titration calorimetry (ITC). The structure of the docked warfarin anion (W-) to Site I is similar to that revealed by X-ray crystallography, with a calculated binding constant of 5.8 x 10(5) M(-1). ITC experiments (pH 7.13 and I = 0.1) carried out in three different buffers (MOPs, phosphate and Tris) reveal binding of W- is accompanied by uptake of 0.30+/-0.02 protons from the solvent. This measurement suggests that the binding of W- is stabilized by an ion-pair interaction between protonated H242 and the phenoxide group of W-.
Perry, JL; Goldsmith, MR; Williams, TR; Radack, KP; Christensen, T; Gorham, J; Pasquinelli, MA; Toone, EJ; Beratan, DN; Simon, JD
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