Evidence for histidine in the triethyltin-binding site of rat haemoglobin

Abstract

One molecule of rat haemoglobin binds two molecules of triethyltin. The binding sites are located on the globin and there is co-operativity between the sites such that the intrinsic affinity constant at pH8·0 increases from 3·5×105m−1 for the binding of the first triethyltin molecule to 5·0×105m−1 for the binding of the second. Evidence is presented, from pH studies and the kinetics of inhibition due to photo-oxidation, that each binding site contains two histidine residues.