Mössbauer studies of the membrane-associated methane monooxygenase from Methylococcus capsulatus bath: evidence for a Diiron center. J Am Chem Soc 2007 Dec 26;129(51):15783-5
Date
12/07/2007Pubmed ID
18052283Pubmed Central ID
PMC2533734DOI
10.1021/ja077682bScopus ID
2-s2.0-37549052557 (requires institutional sign-in at Scopus site) 90 CitationsAbstract
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-mu-hydroxo-bridged diiron cluster. X-ray crystallographic studies of the particulate enzyme, pMMO, have identified two copper centers on the alpha subunit (pmoB) of the alphabetagamma trimer and a site at the interface of the betagamma subunits filled by a Zn, apparently from the crystallization buffer. In our hands, pMMO preparations containing 1-2 iron atoms per alphabetagamma show the highest catalytic activity. We have employed Mössbauer 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 alphabetagamma 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.
Author List
Martinho M, Choi DW, Dispirito AA, Antholine WE, Semrau JD, Münck EMESH terms used to index this publication - Major topics in bold
CatalysisCrystallography, X-Ray
Electron Spin Resonance Spectroscopy
Iron
Methylococcus capsulatus
Oxygenases
Spectrophotometry, Ultraviolet
Spectroscopy, Mossbauer
