Probing the binding interaction between cadmium(II) chloride and lysozyme

The direct binding of cadmium with lysozyme might cause the structural and functional changes of lysozyme. To better understand the potential toxicity and toxic mechanisms of cadmium, it is of vital importance to characterize the interaction of cadmium with lysozyme. This article investigated the interaction of cadmium chloride (CdCl2) with lysozyme using biophysical methods including the spectroscopic technique, isothermal titration calorimetry (ITC), molecular docking and dynamics simulation studies, and enzyme activity measurements. ITC measurements indicated that the interaction is mainly driven by hydrophobic forces with approximately 3 thermodynamic identical binding sites at 310.15 K. Multi-spectroscopic measurements showed that CdCl2 statically quenched the intrinsic fluorescence of lysozyme, formed complexes with lysozyme and altered its secondary structure. Also, the topology of lysozyme in the presence of CdCl2 was altered. Although complexes were formed, we observed no change of lysozyme activity at low CdCl2 concentration because CdCl2 does not preferentially bind to the active site of lysozyme.