Determination by X-ray absorption spectroscopy of the Fe-Fe separation in the oxidized form of the hydrxylase of methane monooxygenase alone and in the presence of MMOD

D.J. Rudd, M.H. Sazinsky, M. Merkx, S.J. Lippard, B. Hedman, K.O. Hodgson

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Abstract

The diiron active site in the hydroxylase of Methylococcus capsulatus (Bath) methane monooxygenase (MMOH) has been studied in the oxidized form by X-ray absorption spectroscopy (XAS). Previous investigations by XAS and X-ray crystallography have identified two different distances (3.0 and 3.4 Å) between the two Fe atoms in the dinuclear site. The present study has employed a systematic extended X-ray absorption fine structure (EXAFS) fitting methodology, utilizing known and simulated active site and relevant model structures, to determine unambiguously the Fe-Fe separation in the oxidized form of MMOH. Consistent and unique fits were only possible for an Fe-Fe distance of 3.0 Å. This methodology was then applied to study potential changes in the active site local structure in the presence of MMOD, a protein of unknown function in multicomponent MMO. Fe K-edge and EXAFS analyses revealed negligible changes in the diiron site electronic and geometric structure upon addition of MMOD to oxidized MMOH.
Original languageEnglish
Pages (from-to)4579-4589
JournalInorganic Chemistry
Volume43
Issue number15
DOIs
Publication statusPublished - 2004

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