Document Detail

Crystal structure of the hydroxylase component of methane monooxygenase from Methylosinus trichosporium OB3b.
MedLine Citation:
PMID:  9070438     Owner:  NLM     Status:  MEDLINE    
Methane monooxygenase (MMO), found in aerobic methanotrophic bacteria, catalyzes the O2-dependent conversion of methane to methanol. The soluble form of the enzyme (sMMO) consists of three components: a reductase, a regulatory "B" component (MMOB), and a hydroxylase component (MMOH), which contains a hydroxo-bridged dinuclear iron cluster. Two genera of methanotrophs, termed Type X and Type II, which differ markedly in cellular and metabolic characteristics, are known to produce the sMMO. The structure of MMOH from the Type X methanotroph Methylococcus capsulatus Bath (MMO Bath) has been reported recently. Two different structures were found for the essential diiron cluster, depending upon the temperature at which the diffraction data were collected. In order to extend the structural studies to the Type II methanotrophs and to determine whether one of the two known MMOH structures is generally applicable to the MMOH family, we have determined the crystal structure of the MMOH from Type II Methylosinus trichosporium OB3b (MMO OB3b) in two crystal forms to 2.0 A resolution, respectively, both determined at 18 degrees C. The crystal forms differ in that MMOB was present during crystallization of the second form. Both crystal forms, however, yielded very similar results for the structure of the MMOH. Most of the major structural features of the MMOH Bath were also maintained with high fidelity. The two irons of the active site cluster of MMOH OB3b are bridged by two OH (or one OH and one H2O), as well as both carboxylate oxygens of Glu alpha 144. This bis-mu-hydroxo-bridged "diamond core" structure, with a short Fe-Fe distance of 2.99 A, is unique for the resting state of proteins containing analogous diiron clusters, and is very similar to the structure reported for the cluster from flash frozen (-160 degrees C) crystals of MMOH Bath, suggesting a common active site structure for the soluble MMOHs. The high-resolution structure of MMOH OB3b indicates 26 consecutive amino acid sequence differences in the beta chain when compared to the previously reported sequence inferred from the cloned gene. Fifteen additional sequence differences distributed randomly over the three chains were also observed, including D alpha 209E, a ligand of one of the irons.
N Elango; R Radhakrishnan; W A Froland; B J Wallar; C A Earhart; J D Lipscomb; D H Ohlendorf
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Protein science : a publication of the Protein Society     Volume:  6     ISSN:  0961-8368     ISO Abbreviation:  Protein Sci.     Publication Date:  1997 Mar 
Date Detail:
Created Date:  1997-05-27     Completed Date:  1997-05-27     Revised Date:  2010-09-10    
Medline Journal Info:
Nlm Unique ID:  9211750     Medline TA:  Protein Sci     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  556-68     Citation Subset:  IM    
Department of Biochemistry, Medical School, University of Minnesota, Minneapolis 55455, USA.
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MeSH Terms
Amino Acid Sequence
Binding Sites
Camphor 5-Monooxygenase / chemistry,  metabolism
Methanococcaceae / enzymology*
Mixed Function Oxygenases / chemistry*
Molecular Sequence Data
Oxygenases / chemistry*,  metabolism
Protein Conformation
Sequence Homology, Amino Acid
Grant Support
Reg. No./Substance:
EC 1.-/Mixed Function Oxygenases; EC 1.13.-/Oxygenases; EC monooxygenase; EC 5-Monooxygenase

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