Mechanism of binding of warfarin enantiomers to recombinant domains of human albumin

Twine, S.M., Gore, M.G., Morton, P., Fish, B.C., Lee, A.G. and East, J.M. (2003) Mechanism of binding of warfarin enantiomers to recombinant domains of human albumin. Archives of Biochemistry and Biophysics, 414 (1), 83-90. (doi:10.1016/S0003-9861(03)00173-5).

Abstract

Domain fragments of human serum albumin corresponding to domains 1 and 2 (D12) and domains 2 and 3 (D23) were expressed in yeast. The kinetics of warfarin binding to these fragments were investigated using stopped-flow fluorescence spectroscopy. Binding can be characterized by a two-step process, a rapid diffusion-controlled step and a slower rate-limiting step in which a stable drug-protein complex is formed. The equilibrium constant for step 1 is greater for both D12 and D23 than for albumin, probably as a result of reduced steric hindrance offered by the domain fragments. Binding step 2, thought to be the result of a conformational change as warfarin is accommodated by the protein, is faster for D12 and D23. Albumin and the domain fragments show an increased preference for the R enantiomer, but the preference is particularly enhanced for domain fragment D12. These preferences can largely be explained by the domains having different rates for step 2 of the binding process.

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