TY - JOUR
T1 - Exploring the terminal region of the proton pathway in the bacterial nitric oxide reductase
AU - Flock, Ulrika
AU - Lachmann, Peter
AU - Reimann, Joachim
AU - Watmough, Nicholas J.
AU - Ädelroth, Pia
PY - 2009
Y1 - 2009
N2 - 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.
AB - 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.
U2 - 10.1016/j.jinorgbio.2009.02.008
DO - 10.1016/j.jinorgbio.2009.02.008
M3 - Article
VL - 103
SP - 845
EP - 850
JO - Journal of Inorganic Biochemistry
JF - Journal of Inorganic Biochemistry
SN - 0162-0134
ER -