Biochemical studies on the relationship between Clostridium perfringens alpha toxin and CTP-binding protein in rabbit erythrocytes.

用中性氨基酸（丙氨酸、亮氨酸和甘氨酸）代替产气荚膜梭菌α毒素中的9个组氨酸残基，研究了毒素中组氨酸残基或锌离子与毒素生物活性的关系。结果表明，毒素中的组氨酸-11残基是毒素蛋白必不可少的组成部分，组氨酸-68、-126和136残基结合了一种可交换的、不稳定的二价金属，这是与膜和底物结合的重要组成部分，组氨酸-148残基紧密结合了一种锌金属，这是α毒素活性或催化位点所必需的。

We replaced all nine histidine residues in Clostridium perfringens alpha toxin with neutral amino acids (alanine, leucine and glycine) by site-direct mutagenesis and investigated the relationship between the biological activities and histidine residues or zinc ion in the toxin.The results suggested that the histidine-11 residue in the toxin is regarded as an essential and integral part of the toxin protein, that the histidine-68, -126 and 136 residues bind an exchangeable and labile divalent metal which is important for binding to membranes and substrates and that the histidine-148 residue tightly binds one zinc metal which is essential for the active or catalytic site of alpha toxin.