Sattler J, Wiegandt H
Eur J Biochem. 1975 Sep 1;57(1):309-16. doi: 10.1111/j.1432-1033.1975.tb02302.x.
The two choleragen protein constituents were isolated and characterized. Protein I has a molecular weight of approximately 54000. It consists of subunits of approximate molecular weight 10000. Protein II with molecular weight of approximately 32000 is cleaved by 2-mercaptoethanol into two fragments, protein II1 (N-terminal Asx, Mr = 25000) and protein II2 (N-terminal Ser, Mr = 7000). Proteins II1 and II2 could be recombined by oxidation to yield protein II. Upon treatment of choleragem with 2-mercaptoethanol protein II1 precipitates quantitatively. The remaining protein consisting of proteins I and II2, was quantitatively precipitated by ganglioside GGtet1. Of the separated choleragen subunit proteins, only protein I and not protein II complexed specifically with ganglioside GGtet1. The isolated proteins I and II were considerably less toxic in the skin test but almost full toxicity was recovered after mixing the two proteins I and II. Antisera against protein I and protein II revealed no immuno-cross reactivity between the two proteins. Both antisera inhibited the biological effects of choleragen in the skin and ileal loop tests. A molecular model for the constitution of choleragen is proposed.
分离并鉴定了霍乱毒素的两种蛋白质成分。蛋白质I的分子量约为54000。它由分子量约为10000的亚基组成。分子量约为32000的蛋白质II被2-巯基乙醇裂解为两个片段，即蛋白质II1（N端为天冬酰胺，Mr = 25000）和蛋白质II2（N端为丝氨酸，Mr = 7000）。蛋白质II1和II2可通过氧化重新组合生成蛋白质II。用2-巯基乙醇处理霍乱毒素时，蛋白质II1会定量沉淀。由蛋白质I和II2组成的剩余蛋白质可被神经节苷脂GGtet1定量沉淀。在分离出的霍乱毒素亚基蛋白中，只有蛋白质I能与神经节苷脂GGtet1特异性结合，而蛋白质II不能。分离出的蛋白质I和II在皮肤试验中的毒性明显较低，但将蛋白质I和II混合后，几乎可恢复全部毒性。抗蛋白质I和抗蛋白质II的抗血清显示这两种蛋白质之间没有免疫交叉反应。两种抗血清在皮肤和回肠袢试验中均能抑制霍乱毒素的生物学效应。本文提出了霍乱毒素组成的分子模型。
