Purification of the STB enterotoxin of Escherichia coli and the role of selected amino acids on its secretion, stability and toxicity.
Purification of the STB enterotoxin of Escherichia coli and the role of selected amino acids on its secretion, stability and toxicity.
复制标题
大肠杆菌STB肠毒素的纯化以及所选氨基酸对其分泌、稳定性和毒性的作用。
DOI：
10.1111/j.1365-2958.1992.tb01414.x
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发表时间：
1992
影响因子：
3.6
通讯作者：
Drefus,LA
中科院分区：
文献类型：
--
作者：
Dreyfus,LA;Urban,RG;Whipp,SC;Slaughter,C;Tachias,K;Kupersztoch,YM;Drefus,LA
对大肠杆菌不溶于甲醇的热稳定肠毒素（STB）进行了纯化，并通过自动Edman降解和胰蛋白酶肽分析进行了表征。氨基末端残基Ser-24证实，从基因序列推断的前23个氨基酸在通过大肠杆菌的转运过程中被去除。大肠杆菌内膜结合自动Edman降解的胰蛋白酶肽分析显示，残基Cys-33和Cys-71之间以及Cys-44和Cys-59之间形成了二硫键。对STB基因进行的寡核苷酸定向诱变表明，二硫键形成并不先于多肽通过内膜的易位，二硫桥形成是周质事件;显然，消除STBrenders的两个二硫键中的任何一个，分子对周质蛋白水解敏感。此外，由Cys-44-Cys-59键定义的环含有STQ毒性活性所需的至少两个氨基酸（Arg-52和Asp-53）。
The methanol‐insolouble heat‐stable enterotoxin ofEscherichia coli(STB) was purified and characterized by automated Edman degradation and tryptic peptide analysis. The amino‐terminal residue, Ser‐24, confirmed that the first 23 amino acids inferred from the gene sequence were removed during translocation through theE. coliinner membrane. Tryptic peptide analysis coupled with automated Edman degradation revealed that disulphide bonds are formed between residues Cys‐33 and Cys‐71 and between Cys‐44 and Cys‐59. Oligonucleotide‐directed mutagenesis performed on the STBgene demonstrated that disulphide bond formation does not precede translocation of the polypeptide through the inner membrane and that disulphide bridge formation is a periplasmic event; apparently, elimination of either of two disulphides of STBrenders the molecule susceptible to periplasmic proteolysis. In addition, a loop defined by the Cys‐44—Cys‐59 bond contains at least two amino acids (Arg‐52 and Asp‐53) required for STQ toxic activity.