Chang C C, Kawata Y, Sakiyama F, Hayashi K
Institute for Protein Research, Osaka University, Japan.
Eur J Biochem. 1990 Oct 24;193(2):567-72. doi: 10.1111/j.1432-1033.1990.tb19373.x.
Ozone oxidation converted the single, invariant, tryptophan residue to N2-formylkynurenine in alpha-bungarotoxin and cobrotoxin. Upon this modification, the lethal toxicity was significantly reduced in cobrotoxin but mostly retained in alpha-bungarotoxin. Each neurotoxin containing kynurenine instead of tryptophan retained the same antigenicity as the native toxin. Fluorescence and CD spectroscopy revealed that, although the environment and state of the kynurenine residue were similar, [Kyn29]cobrotoxin was much more sensitive to pH change than alpha-[Kyn28]bungarotoxin. In terms of lethal toxicity and conformational stability, the invariant tryptophan residue appears to play a more important role in cobrotoxin, imparting a higher lethal toxicity than that in alpha-bungarotoxin, which has a disulfide bond at Cys29-Cys33.
臭氧氧化将α-银环蛇毒素和眼镜蛇毒素中单一、不变的色氨酸残基转化为N2-甲酰犬尿氨酸。经过这种修饰后，眼镜蛇毒素的致死毒性显著降低，但α-银环蛇毒素大多保留了该毒性。每种含有犬尿氨酸而非色氨酸的神经毒素都保留了与天然毒素相同的抗原性。荧光和圆二色光谱表明，尽管犬尿氨酸残基的环境和状态相似，但[Kyn29]眼镜蛇毒素比α-[Kyn28]银环蛇毒素对pH变化更敏感。就致死毒性和构象稳定性而言，不变的色氨酸残基似乎在眼镜蛇毒素中发挥着更重要的作用，赋予其比α-银环蛇毒素更高的致死毒性，α-银环蛇毒素在Cys29-Cys33处有一个二硫键。
