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首页> 外文期刊>Infection and immunity >Mapping the minimal contiguous gene segment that encodes functionally active Shiga-like toxin II.
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Mapping the minimal contiguous gene segment that encodes functionally active Shiga-like toxin II.

机译：映射最小的连续基因片段，该片段编码功能活跃的志贺样毒素II。

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摘要

Shiga-like toxin type II (SLT-II) is one of two antigenically distinct cytotoxins produced by enterohemorrhagic Escherichia coli that are believed to play a central role in the pathogenesis of enterohemorrhagic E. coli-induced disease. SLT-II is a bipartite toxin with an enzymatically active A subunit that inhibits protein synthesis and an oligomeric B subunit that binds to the glycolipid globotriaosylceramide on eukaryotic cells. In this study, functional boundaries of the slt-II operon were mapped. Mutant proteins lacking the last four amino acids from the carboxy terminus of the 70-amino-acid mature SLT-II B polypeptide had no cytotoxic activity. However, when only two amino acids were removed from the carboxy terminus of the B subunit, the cytotoxic activity of the holotoxin was not altered drastically. Furthermore, a 21-amino-acid extension to the carboxy terminus of the SLT-II B polypeptide was tolerated with a minimum reduction in cytotoxic activity of the holotoxin. Deletion of the region coding for amino acids 3 through 18 of the 296-amino-acid mature SLT-II A polypeptide resulted in complete ablation of the cytotoxic activity of the holotoxin as well as abolition of the enzymatic activity of the A subunit. Thus, it appears that both 5'- and 3'-terminal coding sequences are essential for function of the slt-II operon.
机译：志贺样毒素II型（SLT-II）是肠出血性大肠杆菌产生的两种抗原性不同的细胞毒素之一，据信在肠出血性大肠杆菌诱导的疾病的发病机理中起着关键作用。 SLT-II是一种双方毒素，具有抑制蛋白质合成的酶活性A亚基和与真核细胞上糖脂球果糖基神经酰胺结合的寡聚B亚基。在这项研究中，slt-II操纵子的功能边界被映射。缺少70个氨基酸的成熟SLT-II B多肽羧基末端的最后四个氨基酸的突变蛋白没有细胞毒活性。然而，当仅从B亚基的羧基末端除去两个氨基酸时，全毒素的细胞毒性活性没有急剧改变。此外，耐受了SLT-II B多肽的羧基末端的21个氨基酸的延伸，而使全毒素的细胞毒性活性降低到最小。删除编码296个氨基酸的成熟SLT-II A多肽的3至18位氨基酸的区域导致完全清除了全毒素的细胞毒活性以及消除了A亚基的酶促活性。因此，看来5′和3′末端编码序列对于slt-II操纵子的功能都是必不可少的。

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