Exploring the terminal region of the proton pathway in the bacterial nitric oxide reductase

Flock, Ulrika, Lachmann, Peter, Reimann, Joachim, Watmough, Nicholas J. and Ädelroth, Pia (2009) Exploring the terminal region of the proton pathway in the bacterial nitric oxide reductase. Journal of Inorganic Biochemistry, 103. pp. 845-850. ISSN 1873-3344

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Abstract

The c-type nitric oxide reductase (cNOR) from Paracoccus (P.) denitrificans is an integral membrane protein that catalyzes NO reduction; 2NO + 2e− + 2H+ → N2O + H2O. It is also capable of catalyzing the reduction of oxygen to water, albeit more slowly than NO reduction. cNORs are divergent members of the heme–copper oxidase superfamily (HCuOs) which reduce NO, do not pump protons, and the reaction they catalyse is non-electrogenic. All known cNORs have been shown to have five conserved glutamates (E) in the catalytic subunit, by P. denitrificans numbering, the E122, E125, E198, E202 and E267. The E122 and E125 are presumed to face the periplasm and the E198, E202 and E267 are located in the interior of the membrane, close to the catalytic site. We recently showed that the E122 and E125 define the entry point of the proton pathway leading from the periplasm into the active site [U. Flock, F.H. Thorndycroft, A.D. Matorin, D.J. Richardson, N.J. Watmough, P. Ädelroth, J. Biol. Chem. 283 (2008) 3839–3845]. Here we present results from the reaction between fully reduced NOR and oxygen on the alanine variants of the E198, E202 and E267. The initial binding of O2 to the active site was unaffected by these mutations. In contrast, proton uptake to the bound O2 was significantly inhibited in both the E198A and E267A variants, whilst the E202A NOR behaved essentially as wildtype. We propose that the E198 and E267 are involved in terminating the proton pathway in the region close to the active site in NOR.

Item Type:	Article
Faculty \ School:	Faculty of Science > School of Biological Sciences
UEA Research Groups:	Faculty of Science > Research Groups > Molecular Microbiology Faculty of Science > Research Centres > Centre for Molecular and Structural Biochemistry
Depositing User:	EPrints Services
Date Deposited:	01 Oct 2010 13:36
Last Modified:	24 Sep 2024 09:21
URI:	https://ueaeprints.uea.ac.uk/id/eprint/296
DOI:	10.1016/j.jinorgbio.2009.02.008

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