Ikigai H, Ono T, Nakae T, Otsuru H, Shimamura T
Department of Microbiology and Immunology, Showa University School of Medicine, Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
Biochim Biophys Acta. 1999 Jan 8;1415(2):297-305. doi: 10.1016/s0005-2736(98)00183-7.
Vibrio cholerae O1 grown in heart infusion broth produces two forms of El Tor hemolysin (ETH) monomers of 65 and 50 kDa. These monomers form several different sizes of mixed oligomers ranging from 180 to 280 kDa in the liposomal membranes. We found that the N-terminal amino acid sequences, NH2-Trp-Pro-Ala-Pro-Ala-Asn-Ser-Glu, of both the 65- and 50-kDa toxins were identical. We assumed, therefore, that the 65- and 50-kDa toxins were derivatives of the identical precursor protein and the 50-kDa protein was a truncated derivative of 65-kDa ETH. To substantiate this assumption, we treated the 260-kDa oligomer with trypsin and obtained a 190-kDa oligomer. This 190-kDa oligomer consisted of only the 50-kDa subunits. Both 260- and 190-kDa oligomers formed ion channels indistinguishable from each other in planar lipid bilayers. These results suggest that the essential part of the ETH in forming the membrane-damaging aggregate is a 50-kDa protein.
在心脏浸液肉汤中培养的霍乱弧菌O1产生两种形式的埃尔托溶血素（ETH）单体，分子量分别为65 kDa和50 kDa。这些单体在脂质体膜中形成几种不同大小的混合寡聚体，分子量范围从180 kDa到280 kDa。我们发现，65 kDa和50 kDa毒素的N端氨基酸序列NH2-Trp-Pro-Ala-Pro-Ala-Asn-Ser-Glu是相同的。因此，我们推测65 kDa和50 kDa毒素是同一前体蛋白的衍生物，50 kDa蛋白是65 kDa ETH的截短衍生物。为了证实这一推测，我们用胰蛋白酶处理260 kDa的寡聚体，得到了190 kDa的寡聚体。这种190 kDa的寡聚体仅由50 kDa的亚基组成。260 kDa和190 kDa的寡聚体在平面脂质双分子层中形成的离子通道彼此无法区分。这些结果表明，ETH形成膜损伤聚集体的关键部分是50 kDa的蛋白。
