X-ray crystal structures of Moorella thermoacetica FprA. novel diiron site structure and mechanistic insights into a scavenging nitric oxide reductase
X-ray crystal structures of Moorella thermoacetica FprA. novel diiron site structure and mechanistic insights into a scavenging nitric oxide reductase
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DOI：
10.1021/bi0473049
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发表时间：
2005-05-03
期刊：
影响因子：
2.9
通讯作者：
Lanzilotta, WN
中科院分区：
文献类型：
--
作者：
Silaghi-Dumitrescu, R;Kurtz, DM;Lanzilotta, WN
广泛存在的细菌和古细菌金属黄蛋白类的几个成员，称为FprA，可能具有清除一氧化氮还原酶（S-NORs）的功能。然而，唯一已发表的FprA的x射线晶体结构是一种蛋白质，其特征为红氧还毒素：来自Desulfovibrio gigas的二氧氧化还原酶（ROO）。因此，已经确定具有S-NOR功能的Moorella thermoacetica FprA的晶体结构以三种不同的状态解决：分离态、还原态和还原态、no反应态。与D. gigas ROO的情况一样，M. thermoacetica FprA含有一个溶剂桥接的非血红素、非硫二铁位点，其五坐标铁中心由天冬氨酸和末端的谷氨酸、天冬氨酸和组氨酸配体桥接。然而，M. thermoacetica FprA双铁位点在所有三种状态下都显示了四个he配体，每个铁两个，而D. gigas ROO双铁位点据报道只包含三个he配体，尽管第四个he残基是保守的。M. thermoacetica FprA双铁位点内的Fe1-Fe2距离保持在3.2 ~ 3.4埃，三种不同状态下蛋白配体很少或没有运动，两个近端开放配位位点保持不变。分子模型表明，每个开放配位位点都可以容纳端上NO。这种相对刚性和对称的二铁位点结构与二硝基二铁的形成是一致的，二硝基二铁是导致N2O形成的承诺催化中间体。这些结果为微调生物非血红素双铁位点的双氧激活与一氧化氮还原的结构特征提供了新的见解。
Several members of a widespread class of bacterial and archaeal metalloflavoproteins, called FprA, likely function as scavenging nitric oxide reductases (S-NORs). However, the only published X-ray crystal structure of an FprA is for a protein characterized as a rubredoxin:dioxygen oxidoreductase (ROO) from Desulfovibrio gigas. Therefore, the crystal structure of Moorella thermoacetica FprA, which has been established to function as an S-NOR, was solved in three different states: as isolated, reduced, and reduced, NO-reacted. As is the case for D. gigas ROO, the M. thermoacetica FprA contains a solvent-bridged non-heme, non-sulfur diiron site with five-coordinate iron centers bridged by an aspartate, and terminal glutamate, aspartate, and histidine ligands. However, the M. thermoacetica FprA diiron site showed four His ligands, two to each iron, in all three states, whereas the D. gigas ROO diiron site was reported to contain only three His ligands, even though the fourth His residue is conserved. The Fe1-Fe2 distance within the diiron site of M. thermoacetica FprA remained at 3.2-3.4 angstrom with little or no movement of the protein ligands in the three different states and with conservation of the two proximal open coordination sites. Molecular modeling indicated that each open coordination site can accommodate an end-on NO. This relatively rigid and symmetrical diiron site structure is consistent with formation of a diferrous dinitrosyl as the committed catalytic intermediate leading to formation of N2O. These results provide new insight into the structural features that fine-tune biological non-heme diiron sites for dioxygen activation vs nitric oxide reduction.