A single acidic residue can guide binding site selection but does not govern QacR cationic-drug affinity.
A single acidic residue can guide binding site selection but does not govern QacR cationic-drug affinity.
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DOI：
10.1371/journal.pone.0015974
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发表时间：
2011-01-17
期刊：
影响因子：
3.7
通讯作者：
Brown MH
中科院分区：
文献类型：
--
作者：
Peters KM;Brooks BE;Schumacher MA;Skurray RA;Brennan RG;Brown MH
多药结合抑制蛋白QacR与一价和二价阳离子药物的结构表明，E90和E120的羧酸侧链靠近配体乙啶、孔雀石绿和罗丹明6G的正电荷氮，因此可能有助于药物中和和结合亲和力。在这里，我们报告了取代这些谷氨酸残基的结构、生化和体内效应。出乎意料的是，取代对配体亲和力或体内诱导能力几乎没有影响。含有乙胺或孔雀石绿的QacR（E90Q）和QacR（E120Q）的结构具有类似的整体构象，与之前描述的QacR-药物复合物明显不同，但仍然禁止与同源DNA结合。引人注目的是，QacR(E90Q)-罗丹明6G复合物揭示了两个相互排斥的罗丹明6G结合位点。尽管存在多种结构变化，但所有药物结合基本上都是等能结合。因此，这些数据强烈表明，排列在QacR多药物结合口袋中的酸性残基的作用主要是吸引和引导阳离子药物到口袋内引发QacR诱导的“最佳可用”位置，而不是对配体结合亲和力有显著贡献。
Structures of the multidrug-binding repressor protein QacR with monovalent and bivalent cationic drugs revealed that the carboxylate side-chains of E90 and E120 were proximal to the positively charged nitrogens of the ligands ethidium, malachite green and rhodamine 6G, and therefore may contribute to drug neutralization and binding affinity. Here, we report structural, biochemical and in vivo effects of substituting these glutamate residues. Unexpectedly, substitutions had little impact on ligand affinity or in vivo induction capabilities. Structures of QacR(E90Q) and QacR(E120Q) with ethidium or malachite green took similar global conformations that differed significantly from all previously described QacR-drug complexes but still prohibited binding to cognate DNA. Strikingly, the QacR(E90Q)-rhodamine 6G complex revealed two mutually exclusive rhodamine 6G binding sites. Despite multiple structural changes, all drug binding was essentially isoenergetic. Thus, these data strongly suggest that rather than contributing significantly to ligand binding affinity, the role of acidic residues lining the QacR multidrug-binding pocket is primarily to attract and guide cationic drugs to the “best available” positions within the pocket that elicit QacR induction.
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DOI：
10.1107/s0907444904019158
发表时间：
2004-12-01
影响因子：
2.2
作者：
Emsley, P;Cowtan, K
通讯作者：
Cowtan, K
影响因子：
4.9
作者：
KAATZ, GW;SEO, SM
通讯作者：
SEO, SM
影响因子：
5.6
作者：
Alguel, Yilmaz;Meng, Cuixiang;Teran, Wilson;Krell, Tino;Ramos, Juan L.;Gallegos, Maria-Trinidad;Zhang, Xiaodong
通讯作者：
Zhang, Xiaodong
DOI：
10.1126/science.1168750
发表时间：
2009-03-27
期刊：
Science (New York, N.Y.)
影响因子：
--
作者：
Aller SG;Yu J;Ward A;Weng Y;Chittaboina S;Zhuo R;Harrell PM;Trinh YT;Zhang Q;Urbatsch IL;Chang G
通讯作者：
Chang G
影响因子：
11.4
作者：
Edgar, R;Bibi, E
通讯作者：
Bibi, E