1887

Abstract

Nitrous oxide (NO) is a potent greenhouse gas that is produced naturally as an intermediate during the process of denitrification carried out by some soil bacteria. It is consumed by nitrous oxide reductase (NOR), the terminal enzyme of the denitrification pathway, which catalyses a reduction reaction to generate dinitrogen. NOR contains two important copper cofactors (Cu and Cu centres) that are essential for activity, and in copper-limited environments, NOR fails to function, contributing to rising levels of atmospheric NO and a major environmental challenge. Here we report studies of , one of eight genes in the cluster of the soil dwelling α-proteobaterium . A Δ deletion mutant failed to reduce NO under both copper-sufficient and copper-limited conditions, demonstrating that NosX plays an essential role in NOR activity. NOR isolated from -deficient cells was found to be unaffected in terms of the assembly of its copper cofactors, and to be active in assays, indicating that NosX is not required for the maturation of the enzyme; in particular, it plays no part in the assembly of either of the Cu and Cu centres. Furthermore, quantitative Reverse Transcription PCR (qRT-PCR) studies showed that NosX does not significantly affect the expression of the NOR-encoding gene. NosX is a homologue of the FAD-binding protein ApbE from , which functions in the flavinylation of another NOR accessory protein, NosR. Thus, it is likely that NosX is a system-specific maturation factor of NosR, and so is indirectly involved in maintaining the reaction cycle of NOR and cellular NO reduction.

Funding
This study was supported by the:
  • Sophie P Bennett , Biotechnology and Biological Sciences Research Council , (Award NRP DTP)
  • Manuel J Soriano-Laguna , EU , (Award 316472)
  • Andrew J Gates , Biotechnology and Biological Sciences Research Council , (Award BB/S008942/1)
  • Andrew J Gates , Biotechnology and Biological Sciences Research Council , (Award BB/M00256X/1)
  • David J Richardson , Biotechnology and Biological Sciences Research Council , (Award BB/L022796/1)
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/content/journal/micro/10.1099/mic.0.000955
2020-09-04
2020-10-20
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