Binding equilibrium study between Mn(II) and HSA or BSA

Abstract

AbstractThe binding of Mn(II) to human serum albumin (HSA) or bovine serum albumin (BSA) has been studied by equilibrium dialysis at physiological pH (7.43). The Scatchard analysis indicates that there are 1.8 and 1.9 strong binding sites of Mn(II) in HSA and BSA, respectively. The successive stability constants which are reported for the first time are obtained by non‐linear least‐squares methods fitting Bjerrum formula. For both Mn(II)‐HSA and Mn(II)‐BSA systems, the order of magnitude of K1 was found to be 104. The analyses of Hill plots and free energy coupling show that the positive cooperative effect was found in bom Mh(II)‐HSA and Mn(II)‐BSA systems. The results of Mn (II) competing with Cu (II) Zn(II), Cd(II) or Ca(II) to bind to HSA or BSA further support the conjecture that there are two strong binding sites of Mn(II) in both HSA and BSA. One is most probably located at the tripeptide segment of N‐terminal sequence of HSA and BSA molecules involving four groups composed of nitrogen atoms, and the fifth coordination atom is the carboxyl oxygen of Asp1. The coordinated atoms of the other are most probably almost all oxygen atoms.