CD and MCD studies of the effects of component B variant binding on the biferrous active site of methane monooxygenase

Mitic, Natasa, Schwartz, Jennifer K., Brazeau, Brian J., Lipscomb, John D. and Solomon, Edward I. (2008) CD and MCD studies of the effects of component B variant binding on the biferrous active site of methane monooxygenase. Biochemistry, 47 32: 8386-8397. doi:10.1021/bi800818w


Author Mitic, Natasa
Schwartz, Jennifer K.
Brazeau, Brian J.
Lipscomb, John D.
Solomon, Edward I.
Title CD and MCD studies of the effects of component B variant binding on the biferrous active site of methane monooxygenase
Journal name Biochemistry   Check publisher's open access policy
ISSN 0006-2960
1520-4995
Publication date 2008-08-12
Sub-type Article (original research)
DOI 10.1021/bi800818w
Volume 47
Issue 32
Start page 8386
End page 8397
Total pages 12
Place of publication Washington, DC United States
Publisher American Chemical Society
Subject 1303 Specialist Studies in Education
Abstract The multicomponent soluble form of methane monooxygenase (sMMO) catalyzes the oxidation of methane through the activation of O2 at a nonheme biferrous center in the hydroxylase component, MMOH. Reactivity is limited without binding of the sMMO effector protein, MMOB. Past studies show that mutations of specific MMOB surface residues cause large changes in the rates of individual steps in the MMOH reaction cycle. To define the structural and mechanistic bases for these observations, CD, MCD, and VTVH MCD spectroscopies coupled with ligand-field (LF) calculations are used to elucidate changes occurring near and at the MMOH biferrous cluster upon binding of MMOB and the MMOB variants. Perturbations to both the CD and MCD are observed upon binding wild-type MMOB and the MMOB variant that similarly increases O2 reactivity. MMOB variants that do not greatly increase O2 reactivity fail to cause one or both of these changes. LF calculations indicate that reorientation of the terminal glutamate on Fe2 reproduces the spectral perturbations in MCD. Although this structural change allows O2 to bridge the diiron site and shifts the redox active orbitals for good overlap, it is not sufficient for enhanced O2 reactivity of the enzyme. Binding of the T111Y-MMOB variant to MMOH induces the MCD, but not CD changes, and causes only a small increase in reactivity. Thus, both the geometric rearrangement at Fe2 (observed in MCD) coupled with a more global conformational change that may control O2 access (probed by CD), induced by MMOB binding, are critical factors in the reactivity of sMMO.
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Chemistry and Molecular Biosciences
 
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