Mosssbauer studies of the membrane-associated methane monooxygenase from Methylococcus capsulatus bath:: Evidence for a diiron center
Mosssbauer studies of the membrane-associated methane monooxygenase from Methylococcus capsulatus bath:: Evidence for a diiron center
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DOI：
10.1021/ja077682b
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发表时间：
2007-12-26
影响因子：
15
通讯作者：
Muenck, Eckard
中科院分区：
文献类型：
--
作者：
Martinho, Marlene;Choi, Dong W.;Muenck, Eckard
已经在甲烷营养细菌中鉴定出两个甲烷单加氧酶（MMO）系统，即可溶性或细胞质MMO和膜相关或颗粒MMO。特征良好的可溶性MMO的活性位点包含BIS-14-Hydroxo桥的二龙群。 X射线的颗粒酶PMMO的晶体学研究已经确定了在alpha beta gampa gamma trimer的Alpha亚基（PMOB）上的两个铜中心，以及位于由Zn填充的Beta Gamma亚基界面的位点，显然是从Zn填充的，显然是从结晶过程中。在我们的手中，每个αβ伽马含有1-2个铁原子的PMMO制剂显示出最高的催化活性。我们已经采用了摩斯鲍尔光谱来表征制剂中的铁，有趣的是，在PMMO中，我们发现具有与抗磁性耦合二烷（III）簇相同的频谱特性的成分。在整个细胞中，我们每个PMMO的Alpha beta伽玛发现了将近1个二氧化中心。在纯化的酶制剂中，似乎只有10％的地点被占据。这些占领与全细胞中纯化的PMMO和PMMO的测量特定活性很好地相关。我们建议正是“ ZN站点”可容纳Active PMMO的Diiron Center。
Two methane monooxygenase (MMO) systems have been identified in methanotrophic bacteria, namely, a soluble or cytoplasmic MMO and a membrane-associated or particulate MMO. The active site of the well-characterized soluble MMO contains a bis-14-hydroxo-bridged diiron cluster. Xray crystallographic studies of the particulate enzyme, pMMO, have identified two copper centers on the alpha subunit (pmoB) of the alpha beta gamma trimer and a site at the interface of the beta gamma subunits filled by a Zn, apparently from the crystallization buffer. In our hands, pMMO preparations containing 1-2 iron atoms per alpha beta gamma show the highest catalytic activity. We have employed Mossbauer spectroscopy to characterize the iron in our preparations, Interestingly, we find in pMMO a component with the same spectral properties as the antiferromagnetically coupled diiron(III) cluster in the soluble enzyme. In whole cells, we find nearly 1 diiron center per alpha beta gamma of pMMO; in purified enzyme preparations, only 10% of the sites appear to be occupied. These occupancies correlate well with the measured specific activities of purified pMMO and pMMO in whole cells. We suggest that it is the "Zn site" that accommodates the diiron center in active pMMO.