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Title: A Dimeric Chlorite Dismutase Exhibits O2-Generating Activity and Acts as a Chlorite Antioxidant in Klebsiella pneumoniae MGH 78578
Authors: Celis, A. I.
Geeraerts, Z.
Ngmenterebo, D.
Machovina, M. M.
Kurker, Richard C.
Rajakumar, K.
Ivancich, A.
Rodgers, K. R.
Lukat-Rodgers, G. S.
DuBois, J. L.
First Published: 1-Dec-2014
Publisher: American Chemical Society
Citation: Biochemistry, 2015, 54 (2), pp 434–446
Abstract: Chlorite dismutases (Clds) convert chlorite to O2 and Cl–, stabilizing heme in the presence of strong oxidants and forming the O═O bond with high efficiency. The enzyme from the pathogen Klebsiella pneumoniae (KpCld) represents a subfamily of Clds that share most of their active site structure with efficient O2-producing Clds, even though they have a truncated monomeric structure, exist as a dimer rather than a pentamer, and come from Gram-negative bacteria without a known need to degrade chlorite. We hypothesized that KpCld, like others in its subfamily, should be able to make O2 and may serve an in vivo antioxidant function. Here, it is demonstrated that it degrades chlorite with limited turnovers relative to the respiratory Clds, in part because of the loss of hypochlorous acid from the active site and destruction of the heme. The observation of hypochlorous acid, the expected leaving group accompanying transfer of an oxygen atom to the ferric heme, is consistent with the more open, solvent-exposed heme environment predicted by spectroscopic measurements and inferred from the crystal structures of related proteins. KpCld is more susceptible to oxidative degradation under turnover conditions than the well-characterized Clds associated with perchlorate respiration. However, wild-type K. pneumoniae has a significant growth advantage in the presence of chlorate relative to a Δcld knockout strain, specifically under nitrate-respiring conditions. This suggests that a physiological function of KpCld may be detoxification of endogenously produced chlorite.
DOI Link: 10.1021/bi501184c
ISSN: 0006-2960
eISSN: 1520-4995
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © 2014 American Chemical Society This is an open access article published under an ACS AuthorChoice License , which permits copying and redistribution of the article or any adaptations for non-commercial purposes.
Description: Further description of K. pneumoniae mutant generation (Figure S1), rR spectra of ferrous KpCld (Figure S2), temperature dependence of the rR spectrum of KpCld (Figure S3), pH–rate profiles (Figure S4), NaOCl/KpCld titration data (Figure S5), reaction between NaOCl and KpCld monitored over time (Figure S6), and reaction between DaCld and chlorite in the presence of MCD (Figure S7). This material is available free of charge via the Internet at
Appears in Collections:Published Articles, Dept. of Infection, Immunity and Inflammation

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