Binding of sodium aurothiomalate to human serum albumin in vitro at physiological conditions.

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Abstract
The binding of aurothiomalate to human serum albumin was studied by equilibrium dialysis at 37 degrees C, pH 7.3-7.4, and ionic strength 0.15-0.16 mol/l. It was found that aurothiomalate was bound to albumin at one site with an apparent association constant K1 = 3.0 X 10(4) M-1 and at three or more sites with the sum of association constants of the order of 10(3) M-1. Valuable information of the aurothiomalate-albumin interaction was deduced from the observed changes of pH of the albumin solutions during dialysis. A conceivable binding mechanism consistent with the results might be that aurothiomalate binds as Au+ to the high affinity binding site by exchanging a H+ and that this site might be the sulphydryl group in cysteine34; and that aurothiomalate binds as monomeric anions to the lower affinity binding sites.