Hovde C J, Marr J C, Hoffmann M L, Hackett S P, Chi Y I, Crum K K, Stevens D L, Stauffacher C V, Bohach G A
Department of Microbiology, Molecular Biology and Biochemistry, University of Idaho, Moscow 83843.
Mol Microbiol. 1994 Sep;13(5):897-909. doi: 10.1111/j.1365-2958.1994.tb00481.x.
The goal of this study was to investigate the role of the disulphide bond of staphylococcal enterotoxin C1 (SEC1) in the structure and activity of the toxin. Mutants unable to form a disulphide bond were generated by substituting alanine or serine for cysteine at positions 93 and/or 110. Although we did not directly investigate the residues between the disulphide linkage, tryptic lability showed that significant native structure in the cystine loop is preserved in the absence of covalent bonding between residues 93 and 110. Since no correlation was observed between the behaviour of these mutants with regard to toxin stability, emesis and T cell proliferation we conclude that SEC1-induced emesis and T cell proliferation are dependent on separate regions of the molecule. The disulphide bond itself is not an absolute requirement for either activity. However, conformation within or adjacent to the loop is important for emesis. Although mutants with alanine substitutions were not emetic, those with serine substitutions retained this activity, suggesting that the disulphide linkage stabilizes a crucial conformation but can be replaced by residues which hydrogen bond.
本研究的目的是探究葡萄球菌肠毒素C1（SEC1）的二硫键在该毒素的结构和活性中的作用。通过将丙氨酸或丝氨酸取代93位和/或110位的半胱氨酸，生成了无法形成二硫键的突变体。尽管我们没有直接研究二硫键连接之间的残基，但胰蛋白酶敏感性表明，在93位和110位残基之间不存在共价键的情况下，胱氨酸环中的显著天然结构得以保留。由于未观察到这些突变体在毒素稳定性、催吐作用和T细胞增殖方面的行为之间存在相关性，我们得出结论，SEC1诱导的催吐作用和T细胞增殖依赖于分子的不同区域。二硫键本身对于任何一种活性都不是绝对必需的。然而，环内或其附近的构象对于催吐作用很重要。尽管用丙氨酸取代的突变体没有催吐活性，但用丝氨酸取代的突变体保留了这种活性，这表明二硫键稳定了一种关键构象，但可以被能够形成氢键的残基所取代。
