Investigations on the effects of Cu super(2+) on the structure and function of human serum albumin

Human serum albumin (HSA) is the most prominent protein in blood plasma with important physiological functions. Although copper is an essential metal for all organisms, the massive utilization of copper has led to concerns regarding its potential health impact. To better understand the potential toxicity and toxic mechanisms of Cu super(2+), it is of vital importance to characterize the interaction of Cu super(2+) with HSA. The effect of Cu super(2+) on the structure and function of HSA in vitro were investigated by biophysical methods including fluorescence techniques, circular dichroism (CD), time-resolved measurements, isothermal titration calorimetry (ITC), molecular simulations and esterase activity assay. Multi-spectroscopic measurements proved that Cu super(2+) quenched the intrinsic fluorescence of HSA in a dynamic process accompanied by the formation of complex and alteration of secondary structure. But the Cu super(2+) had minimal effect on the backbone and secondary structure of HSA at relatively low concentrations. The ITC results indicated Cu super(2+) interacted with HSA spontaneously through hydrophobic forces with approximately 1 thermodynamic identical binding sites at 298K. The esterase activity of HSA was inhibited obviously at the concentration of 810 super(-5)M. However, molecular simulation showed that Cu super(2+) mainly interacted with the amino acid residues Asp (451) by the electrostatic force. Thus, we speculated the interaction between Cu super(2+) and HSA might induce microenvironment of the active site (Arg 410). This study has provided a novel idea to explore the biological toxicity of Cu super(2+) at the molecular level.