Cadmium(II), zinc(II), and copper(II) ions binding to bovine serum albumin. A 113Cd NMR study

Abstract

The interaction between bovine serum albumin and the metals Cd(II), Zn(II) and Cu(II) was studied by 113Cd NMR. A 113Cd titration of the protein revealed two strong Cd(II) binding sites. Competition between Zn(II) (or Cu(II)) and Cd(II) for the strong sites indicates that there is a common strong binding site for Cu(II), Zn(II) and Cd(II), with higher affinity for Cu(II) and Zn(II) than for Cd(II). Competition between serum albumin and NTA for Cd(II) did not allow conclusive evaluation of the intrinsic binding constants, probably due to the formation of ternary complexes NTACd(II)protein. Chemical shifts are in good agreement with histidyl residue involvement in one site, and probably oxygen ligands in a second site. The site responsible for strong binding of Zn(II) contains two histidyl residues, but not thiol groups.