Structure and function of calcineurin B subunit: mutation in the calcium binding site

Effect of mutations in the calcium binding site on calcineurin B subunit structure and function was investigated, by far ultraviolet CD spectrum, ultraviolet difference spectrum, endogenous fluorescence spectrum and ANS fluorescence spectrum．It was found that calcium binding site mutant CNB-Y105W was stronger than wild type CNB to activate CNA, but CNB-E110Q was weaker．The affinity of CNB-Y105W and CNB-E110Q for Ca²⁺ was both found to be lower than CNB．The secondary structures were found to be similar among CNB and the 2 mutants, but their tertiary structures showed significant differences, consistent with their differences in protein activity．