Tang G Q, Iida T, Yamamoto K, Honda T
Department of Bacteriology and Serology, Osaka University, Japan.
Infect Immun. 1994 Aug;62(8):3299-304. doi: 10.1128/iai.62.8.3299-3304.1994.
A mutant toxin, R7, of thermostable direct hemolysin (TDH) with a single amino acid substitution at glycine 62 was analyzed. The hemolytic activity of R7 decreased to less than 1/1,000 of that of wild-type TDH, and its mouse lethality was undetectable. This mutant toxin, however, showed a marked inhibitory effect on hemolysis by wild-type TDH. Enzyme immunoassay and flow cytometric analysis demonstrated that R7 retained approximately 50% of the ability to bind to erythrocytes compared with that of wild-type TDH, suggesting that its inhibition of hemolysis by wild-type TDH might be due to blocking the binding sites on the erythrocyte membrane. Wild-type TDH affected the erythrocyte membrane by causing an influx of calcium and propidium iodide, while R7 showed no detectable effects of these kinds. These results suggest that hemolysis by TDH consists of at least two steps, binding and postbinding, and that R7 is likely to be a postbinding activity-deficient mutant toxin of TDH.
分析了一种热稳定直接溶血素（TDH）的突变毒素R7，其在第62位甘氨酸处有一个氨基酸替换。R7的溶血活性降至野生型TDH的1/1000以下，且未检测到其对小鼠的致死性。然而，这种突变毒素对野生型TDH的溶血作用表现出显著的抑制效果。酶免疫测定和流式细胞术分析表明，与野生型TDH相比，R7保留了约50%与红细胞结合的能力，这表明其对野生型TDH溶血的抑制可能是由于阻断了红细胞膜上的结合位点。野生型TDH通过引起钙和碘化丙啶的内流来影响红细胞膜，而R7未显示出这些可检测的作用。这些结果表明，TDH的溶血作用至少包括两个步骤，即结合和结合后步骤，并且R7可能是TDH的一种结合后活性缺陷型突变毒素。
