Dataset Information

Nitrite-reductase and peroxynitrite isomerization activities of Methanosarcina acetivorans protoglobin.

ABSTRACT: Within the globin superfamily, protoglobins (Pgb) belong phylogenetically to the same cluster of two-domain globin-coupled sensors and single-domain sensor globins. Multiple functional roles have been postulated for Methanosarcina acetivorans Pgb (Ma-Pgb), since the detoxification of reactive nitrogen and oxygen species might co-exist with enzymatic activity(ies) to facilitate the conversion of CO to methane. Here, the nitrite-reductase and peroxynitrite isomerization activities of the CysE20Ser mutant of Ma-Pgb (Ma-Pgb*) are reported and analyzed in parallel with those of related heme-proteins. Kinetics of nitrite-reductase activity of ferrous Ma-Pgb* (Ma-Pgb*-Fe(II)) is biphasic and values of the second-order rate constant for the reduction of NO2- to NO and the concomitant formation of nitrosylated Ma-Pgb*-Fe(II) (Ma-Pgb*-Fe(II)-NO) are k(app1)=?9.6 ± 0.2 M(-1) s(-1) and k(app2) = 1.2 ± 0.1 M(-1) s(-1) (at pH 7.4 and 20 °C). The k(app1) and k(app2) values increase by about one order of magnitude for each pH unit decrease, between pH 8.3 and 6.2, indicating that the reaction requires one proton. On the other hand, kinetics of peroxynitrite isomerization catalyzed by ferric Ma-Pgb* (Ma-Pgb*-Fe(III)) is monophasic and values of the second order rate constant for peroxynitrite isomerization by Ma-Pgb*-Fe(III) and of the first order rate constant for the spontaneous conversion of peroxynitrite to nitrate are h(app)?=?3.8 × 10(4 )M(-1) s(-1) and h0 = 2.8 × 10(-1) s(-1) (at pH 7.4 and 20 °C). The pH-dependence of hon and h0 values reflects the acid-base equilibrium of peroxynitrite (pKa = 6.7 and 6.9, respectively; at 20 °C), indicating that HOONO is the species that reacts preferentially with the heme-Fe(III) atom. These results highlight the potential role of Pgbs in the biosynthesis and scavenging of reactive nitrogen and oxygen species.

SUBMITTER: Ascenzi P

PROVIDER: S-EPMC4020757 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Nitrite-reductase and peroxynitrite isomerization activities of Methanosarcina acetivorans protoglobin.

Ascenzi Paolo P Leboffe Loris L Pesce Alessandra A Ciaccio Chiara C Sbardella Diego D Bolognesi Martino M Coletta Massimo M

PloS one 20140514 5

Within the globin superfamily, protoglobins (Pgb) belong phylogenetically to the same cluster of two-domain globin-coupled sensors and single-domain sensor globins. Multiple functional roles have been postulated for Methanosarcina acetivorans Pgb (Ma-Pgb), since the detoxification of reactive nitrogen and oxygen species might co-exist with enzymatic activity(ies) to facilitate the conversion of CO to methane. Here, the nitrite-reductase and peroxynitrite isomerization activities of the CysE20Ser ...[more]

PMID: 24827820

Similar Datasets

Project description:BackgroundAcetate is the major source of methane in nature. The majority of investigations have focused on acetotrophic methanogens for which energy-conserving electron transport is dependent on the production and consumption of H₂ as an intermediate, although the great majority of acetotrophs are unable to metabolize H₂. The presence of cytochrome c and a complex (Ma-Rnf) homologous to the Rnf (Rhodobacter nitrogen fixation) complexes distributed in the domain Bacteria distinguishes non-H₂-utilizing Methanosarcina acetivorans from H₂-utilizing species suggesting fundamentally different electron transport pathways. Thus, the membrane-bound electron transport chain of acetate-grown M. acetivorans was investigated to advance a more complete understanding of acetotrophic methanogens.ResultsA component of the CO dehydrogenase/acetyl-CoA synthase (CdhAE) was partially purified and shown to reduce a ferredoxin purified using an assay coupling reduction of the ferredoxin to oxidation of CdhAE. Mass spectrometry analysis of the ferredoxin identified the encoding gene among annotations for nine ferredoxins encoded in the genome. Reduction of purified membranes from acetate-grown cells with ferredoxin lead to reduction of membrane-associated multi-heme cytochrome c that was re-oxidized by the addition of either the heterodisulfide of coenzyme M and coenzyme B (CoM-S-S-CoB) or 2-hydoxyphenazine, the soluble analog of methanophenazine (MP). Reduced 2-hydoxyphenazine was re-oxidized by membranes that was dependent on addition of CoM-S-S-CoB. A genomic analysis of Methanosarcina thermophila, a non-H2-utilizing acetotrophic methanogen, identified genes homologous to cytochrome c and the Ma-Rnf complex of M. acetivorans.ConclusionsThe results support roles for ferredoxin, cytochrome c and MP in the energy-conserving electron transport pathway of non-H₂-utilizing acetotrophic methanogens. This is the first report of involvement of a cytochrome c in acetotrophic methanogenesis. The results suggest that diverse acetotrophic Methanosarcina species have evolved diverse membrane-bound electron transport pathways leading from ferredoxin and culminating with MP donating electrons to the heterodisulfide reductase (HdrDE) for reduction of CoM-S-S-CoB.

Dataset Information

Nitrite-reductase and peroxynitrite isomerization activities of Methanosarcina acetivorans protoglobin.

Publications

Nitrite-reductase and peroxynitrite isomerization activities of Methanosarcina acetivorans protoglobin.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets