Chang L S
Department of Biochemistry, Kaohsiung Medical College, Taiwan, ROC.
J Protein Chem. 1996 Jul;15(5):473-80. doi: 10.1007/BF01886855.
Notexin from Notechis scutatus scutatus snake venom was subjected to Lys modification with pyridoxal 5'-phosphate (PLP), and one major modified derivative was purified on a cation-exchanger SP-8HR column. The results of amino acid analysis and sequence determination revealed that only 2 Lys residues at positions 82 and 115 out of 11 Lys residues in notexin were modified. The incorporation of PLP into the protein was accompanied by the loss of 53% lethal toxicity, but the modified notexin showed an about 1.2-fold increase in enzymatic activity. However, the secondary structure of the toxin molecule did not significantly change after modification with PLP as revealed by the CD spectra, and the antigenicity of PLP derivative remained unchanged. The modified derivative retained its affinity for Ca2+, indicating that the modified Lys residues did not participate in Ca2+ binding. These results indicate that modification of Lys residues causes a differential effect on the enzymatic activity and lethal toxicity of notexin, and suggest that notexin might possess two functional sites, one responsible for the catalytic activity and the other associated with its lethal effect.
对盾鳞蝰蛇毒中的诺维毒素进行5'-磷酸吡哆醛（PLP）介导的赖氨酸修饰，并在阳离子交换剂SP - 8HR柱上纯化出一种主要的修饰衍生物。氨基酸分析和序列测定结果显示，诺维毒素11个赖氨酸残基中只有第82位和第115位的2个赖氨酸残基被修饰。PLP掺入蛋白质的同时伴随着53%致死毒性的丧失，但修饰后的诺维毒素酶活性提高了约1.2倍。然而，圆二色光谱显示，PLP修饰后毒素分子的二级结构没有显著变化，PLP衍生物的抗原性也保持不变。修饰后的衍生物保留了对Ca2+的亲和力，表明修饰的赖氨酸残基不参与Ca2+结合。这些结果表明，赖氨酸残基的修饰对诺维毒素的酶活性和致死毒性产生了不同的影响，并提示诺维毒素可能具有两个功能位点，一个负责催化活性，另一个与其致死效应相关。
