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J Biol Chem. 2017 Feb 10;292(6):2485-2494. doi: 10.1074/jbc.M116.752014. Epub 2016 Dec 27.

A Two-component NADPH Oxidase (NOX)-like System in Bacteria Is Involved in the Electron Transfer Chain to the Methionine Sulfoxide Reductase MsrP.

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From the Institut de Biologie Structurale (IBS), Université Grenoble Alpes, 38044 Grenoble.
the IBS, Commissariat à l'Energie Atomique (CEA), 38027 Grenoble.
the IBS, CNRS, 38027 Grenoble.
the Université Grenoble Alpes, Grenoble.
CNRS LCBM UMR 5249, Grenoble, and.
CEA-DRF-BIG-Laboratoire de Chimie et Biologie des Métaux, 17 Rue des Martyrs, 38054 Grenoble, France.
From the Institut de Biologie Structurale (IBS), Université Grenoble Alpes, 38044 Grenoble,


MsrPQ is a newly identified methionine sulfoxide reductase system found in bacteria, which appears to be specifically involved in the repair of periplasmic proteins oxidized by hypochlorous acid. It involves two proteins: a periplasmic one, MsrP, previously named YedY, carrying out the Msr activity, and MsrQ, an integral b-type heme membrane-spanning protein, which acts as the specific electron donor to MsrP. MsrQ, previously named YedZ, was mainly characterized by bioinformatics as a member of the FRD superfamily of heme-containing membrane proteins, which include the NADPH oxidase proteins (NOX/DUOX). Here we report a detailed biochemical characterization of the MsrQ protein from Escherichia coli We optimized conditions for the overexpression and membrane solubilization of an MsrQ-GFP fusion and set up a purification scheme allowing the production of pure MsrQ. Combining UV-visible spectroscopy, heme quantification, and site-directed mutagenesis of histidine residues, we demonstrated that MsrQ is able to bind two b-type hemes through the histidine residues conserved between the MsrQ and NOX protein families. In addition, we identify the E. coli flavin reductase Fre, which is related to the dehydrogenase domain of eukaryotic NOX enzymes, as an efficient cytosolic electron donor to the MsrQ heme moieties. Cross-linking experiments as well as surface Plasmon resonance showed that Fre interacts with MsrQ to form a specific complex. Taken together, these data support the identification of the first prokaryotic two-component protein system related to the eukaryotic NOX family and involved in the reduction of periplasmic oxidized proteins.


Escherichia coli (E. coli); NADPH oxidase; YedZ; electron transfer; flavin mononucleotide (FMN); flavin reductase Fre; heme; membrane protein; methionine sulfide reductase MsrPQ

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