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首页> 外文期刊>Journal of bacteriology >The N Terminus of the Escherichia coli Transcription Activator MalT Is the Domain of Interaction with MalY
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The N Terminus of the Escherichia coli Transcription Activator MalT Is the Domain of Interaction with MalY

机译：大肠杆菌转录激活子MalT的N末端是与MalY相互作用的域

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The maltose system of Escherichia coli consists of a number of genes encoding proteins involved in the uptake and metabolism of maltose and maltodextrins. The system is positively regulated by MalT, its transcriptional activator. MalT activity is controlled by two regulatory circuits: a positive one with maltotriose as effector and a negative one involving several proteins. MalK, the ATP-hydrolyzing subunit of the cognate ABC transporter, MalY, an enzyme with the activity of a cystathionase, and Aes, an acetyl esterase, phenotypically act as repressors of MalT activity. By in vivo titration assays, we have shown that the N-terminal 250 amino acids of MalT contain the interaction site for MalY but not for MalK. This was confirmed by gel filtration analysis, where MalY was shown to coelute with the N-terminal MalT structural domain. Mutants in MalT causing elevated mal gene expression in the absence of exogenous maltodextrins were tested in their response to the three repressors. The different MalT mutations exhibited a various degree of sensitivity towards these repressors, but none was resistant to all of them. Some of them became nearly completely resistant to Aes while still being sensitive to MalY. These mutations are located at positions 38, 220, 243, and 359, most likely defining the interaction patch with Aes on the three-dimensional structure of MalT.
机译：大肠杆菌的麦芽糖系统由许多编码与麦芽糖和麦芽糖糊精的摄取和代谢有关的蛋白质的基因组成。该系统受其转录激活因子MalT的正调控。 MalT活性受两个调节回路控制：阳性的一个以麦芽三糖为效应子，阴性的一个涉及几种蛋白质。在表型上，MalK是同源ABC转运蛋白的ATP水解亚基，MalY是具有胱硫醚酶活性的酶，而Aes是乙酰基酯酶，在表型上起着MalT活性抑制因子的作用。通过体内滴定测定法，我们已经显示，MalT的N端250个氨基酸包含MalY的相互作用位点，但MalK却没有。凝胶过滤分析证实了这一点，其中MalY被证明与N末端MalT结构域共洗脱。在不存在外源麦芽糖糊精的情况下，测试了MalT中导致 mal 基因表达升高的突变体对三种阻遏物的反应。不同的MalT突变对这些阻遏物表现出不同程度的敏感性，但没有一个对所有阻遏物都有抗性。其中一些变得对Aes几乎完全抵抗，同时仍然对MalY敏感。这些突变位于位置38、220、243和359，最有可能在MalT的三维结构上定义与Aes的相互作用。

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