The biological toxicity of uranyl ion (UO
2
2+
) lies in interacting with proteins and disrupting their native functions. The structural and functional consequences of UO
2
2+
interacting with cytochrome b
5 (cyt b
5), a small membrane heme protein, and its heme axial ligand His39Ser variant, cyt b
5 H39S, were investigated both experimentally and theoretically. In experiments, although cyt b
5 was only slightly affected, UO
2
2+
binding to cyt b
5 H39S with a K
D of 2.5 μM resulted in obvious alteration of the heme active site,...
