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-.
Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA.
Jennifer L
JL
Perry
Michael R
MR
Goldsmith
T Richard
TR
Williams
Kyle P
KP
Radack
Trine
T
Christensen
Justin
J
Gorham
Melissa A
MA
Pasquinelli
Eric J
EJ
Toone
David N
DN
Beratan
John D
JD
Simon
D000136:Acid-Base Equilibrium; D001665:Binding Sites; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D012709:Serum Albumin / Q000737:chemistry* / Q000378:metabolism*; D014859:Warfarin / Q000378:metabolism*
D012709:Serum Albumin; D014859:Warfarin