Structures of nitroreductase in three states - Effects of inhibitor binding and reduction
Structures of nitroreductase in three states - Effects of inhibitor binding and reduction
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DOI：
10.1074/jbc.m111334200
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发表时间：
2002-03-29
影响因子：
4.8
通讯作者：
Rodgers, DW
中科院分区：
文献类型：
--
作者：
Haynes, CA;Koder, RL;Rodgers, DW
阴沟肠杆菌硝基还原酶的晶体结构已确定为与苯甲酸盐和乙酸盐抑制剂单独复合物中的氧化形式以及双电子还原形式。硝基还原酶是一组酶的成员，可还原多种硝基芳香族化合物，在化疗和生物修复中具有潜在用途。硝基还原酶二聚体的单体采用α+β折叠并在二聚体界面处一起结合两个黄素单核苷酸辅基。在氧化酶中，黄素环系统采用强烈弯曲（16度）的构象，而在还原形式的酶中，弯曲度增加（25度），大致与溶液中不含还原黄素的预测构象相同。由于游离的氧化黄素是平面的，氧化酶中的诱导弯曲可能有利于还原，并且它也可能解释了酶无法稳定一电子还原的半醌黄素的特征，该黄素也是平面的。两种抑制剂在部分重叠位点结合在嘧啶和黄素中心环上。两种抑制剂复合物的比较表明，螺旋 H6 的一部分可以弯曲以适应不同大小的抑制剂，这表明了适应不同底物的机制。
The crystal structure of the nitroreductase enzyme from Enterobacter cloacae has been determined for the oxidized form in separate complexes with benzoate and acetate inhibitors and for the two-electron reduced form. Nitroreductase is a member of a group of enzymes that reduce a broad range of nitroaromatic compounds and has potential uses in chemotherapy and bioremediation. The monomers of the nitroreductase dimer adopt an alpha+beta fold and together bind two flavin mononucleotide prosthetic groups at the dimer interface. In the oxidized enzyme, the flavin ring system adopts a strongly bent (16degrees) conformation, and the bend increases (25degrees) in the reduced form of the enzyme, roughly the conformation predicted for reduced flavin free in solution. Because free oxidized flavin is planar, the induced bend in the oxidized enzyme may favor reduction, and it may also account for the characteristic inability of the enzyme to stabilize the one electron-reduced semiquinone flavin, which is also planar. Both inhibitors bind over the pyrimidine and central rings of the flavin in partially overlapping sites. Comparison of the two inhibitor complexes shows that a portion of helix H6 can flex to accommodate the differently sized inhibitors suggesting a mechanism for accommodating varied substrates.