The NH2-terminal arms of trp repressor participate in repressor/operator association.
The NH2-terminal arms of trp repressor participate in repressor/operator association.
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trp 阻遏物的 NH2 末端臂参与阻遏物/操纵子的关联。
DOI：
10.1093/nar/20.2.337
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发表时间：
1992
影响因子：
14.9
通讯作者：
Yanofsky,C
中科院分区：
文献类型：
--
作者：
Hurlburt,BK;Yanofsky,C
描述了反阻遏物、去阻遏物和阻遏物/操纵基因复合物的三维结构。蛋白质的NH 2-末端臂包含约12-14个残基，在这些结构中的任何一个中都没有很好地分辨。Carey以前的研究表明，这些臂是完全的玻璃体阻遏物活性所必需的。为了更全面地研究臂的作用，我们去除了trpR基因的密码子2-5和2-8，并在体内和体外分析了所得截短的阻遏物。发现Δ2-5 trp阻遏蛋白的活性约为野生型阻遏蛋白的25%。在体外平衡结合实验中，Δ2-5 trp阻遏物对操纵子结合的活性低5倍。Δ2-5 trp阻遏蛋白与操纵基因形成的复合物的解离速率与野生型trp阻遏蛋白/操纵基因复合物的解离速率基本相同，但Δ2-5 trp阻遏蛋白与操纵基因的结合明显缺陷。由于色氨酸阻遏物的NH 2-末端臂似乎主要影响关联，因此它们可能在促进阻遏物与DNA的非特异性关联中发挥作用，因为阻遏物寻求其同源算子。Δ2-8 trp阻遏物在体内和体外均不稳定，这表明NH 2末端臂的某些部分是分子其余部分正确折叠所必需的。
The 3-dimensionaI structures of thetrprepresser, aporepressor, and repressor/operator complex have been described. The NH2-terminal arms of the protein, comprising approximately 12–14 residues, were not well resolved in any of these structures. Previous studies by Carey showed that the arms are required for fullin vitrorepressor activity. To examine the roles of the arms more fully we have removed codons 2–5 and 2–8 of thetrpRgene and analyzed the resulting truncated repressersin vivoandin vitro. The Δ2–5 trp represser was found to be approximately 25% as active as the wild type represserin vivo. Inin vitroequilibrium binding experiments, the Δ2–5 trp represser was shown to be five-fold less active on operator binding. The rate of dissociation of the complex formed between the Δ2–5 trp represser and operator was essentially the same as the rate of dissociation of the wild type trp repressor/operator complex, However association of the Δ2–5 trp represser with operator was clearly defective. Since the NH2-terminal arms of the trp repressor appear to affect association predominantly they may play a role in facilitating non-specific association of repressor with DNA as represser seeks its cognate operators. The Δ2–8 trp repressor was unstablein vivoandin vitro, suggesting that some portion of the NH2-terminal arm is required for proper folding of the remainder of the molecule.