Structure of RdxA--an oxygen-insensitive nitroreductase essential for metronidazole activation in Helicobacter pylori.
Structure of RdxA--an oxygen-insensitive nitroreductase essential for metronidazole activation in Helicobacter pylori.
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DOI：
10.1111/febs.12020
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发表时间：
2012-12
期刊：
影响因子：
--
通讯作者：
Sancho J
中科院分区：
文献类型：
--
作者：
Martínez-Júlvez M;Rojas AL;Olekhnovich I;Espinosa Angarica V;Hoffman PS;Sancho J
人胃病原体幽门螺杆菌的RdxA氧不敏感性硝基还原酶负责该生物体对氧化还原活性前药甲硝唑（MTZ）的易感性。rdxA中的功能丧失突变是对这种治疗药物耐药的主要原因。RdxA在需氧条件下表现出有效的NADPH氧化酶活性，在严格厌氧条件下表现出甲硝唑还原酶活性。在这里，我们报告的晶体结构的RdxA，这是一个homodimer表现出域交换，并含有两个分子的FMN绑定在二聚体界面。我们已经发现了Tyr 47的侧链和FMN的异咯嗪环之间的间隙，这似乎适合于底物结合。该结构不包括残基97-128，其对应于来自E的NTR的局部不稳定部分。大肠杆菌，并可能参与辅因子结合。幽门螺杆菌RdxA与其他已知结构的氧化还原酶的比较表明，RdxA可能属于一个新的氧化还原酶亚组，其中靠近FMN辅因子的半胱氨酸侧链可能参与还原活性。在这方面，C159突变为A或S（C159 A/S）导致MTZ还原酶活性丧失，但不导致NADPH氧化酶活性丧失。RdxA结构允许解释先前描述的许多功能丧失突变，包括影响C159的突变，C159是MTZ硝基还原所需的与FMN相互作用的残基。我们的研究提供了独特的见解黄素的氧化还原行为在这个关键酶甲硝唑激活，并在基因治疗中的潜在用途。
The RdxA oxygen insensitive nitroreductase of the human gastric pathogen Helicobacter pylori is responsible for the susceptibility of this organism to the redox active prodrug metronidazole (MTZ). Loss-of-function mutations in rdxA are primarily responsible for resistance to this therapeutic. RdxA exhibits potent NADPH oxidase activity under aerobic conditions and metronidazole reductase activity under strictly anaerobic conditions. Here we report the crystal structure of RdxA, which is a homodimer exhibiting domain swapping and containing two molecules of FMN bound at the dimer interface. We have found a gap between the side chain of Tyr47 and the isoalloxazine ring of FMN that seems appropriate for substrate binding. The structure does not include residues 97–128, which corresponds to a locally unstable part of the NTR from E. coli, and might be involved in cofactor binding. Comparison of H pylori RdxA to other oxidoreductases of known structure suggests RdxA may belong to a new subgroup of oxidoreductases in which a cysteine sidechain close to the FMN cofactor could be involved in the reductive activity. In this respect, mutation of C159 to A or S (C159A/S) has resulted in loss of MTZ reductase activity, but not NADPH oxidase activity. The RdxA structure allows interpretation of the many loss-of-function mutations previously described, including those affecting C159, a residue whose interaction with FMN is required for nitroreduction of MTZ. Our studies provide unique insights into the redox behavior of the flavin in this key enzyme for metronidazole activation, and with potential use in gene therapy.
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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：
4.8
作者：
Haynes, CA;Koder, RL;Rodgers, DW
通讯作者：
Rodgers, DW
影响因子：
3.2
作者：
LeBlanc, Jason J.;Brassinga, Ann Karen C.;Hoffman, Paul S.
通讯作者：
Hoffman, Paul S.
影响因子：
5.6
作者：
Lovering, AL;Hyde, EI;White, SA
通讯作者：
White, SA
影响因子：
5.6
作者：
Gough, J;Karplus, K;Chothia, C
通讯作者：
Chothia, C