nosZ encodes nitrous-oxide reductase, the copper enzyme that reduces nitrous oxide to dinitrogen in the terminal N2O-reduction step of denitrification or nitrogen oxide respiration.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004129 cytochrome-c oxidase activity | IEA GO_REF:0000002 | REMOVE | Summary: REMOVE. NosZ is a nitrous-oxide reductase, not cytochrome-c oxidase. The specific nitrous-oxide reductase activity annotation is present. Reason: The cytochrome-c oxidase activity term appears to come from a shared cytochrome oxidase subunit II-like copper-binding domain. The protein assignment, EC number, HAMAP model, and PANTHER subfamily all identify this sequence as nitrous-oxide reductase, so GO:0050304 is the correct MF. Family research confirms that PTHR42838 can conflate NosZ with cytochrome c oxidase subunit II because both carry CuA-related domains. Proposed replacements: nitrous-oxide reductase activity Supporting Evidence: file:RHOPA/nosZ/nosZ-uniprot.txt RecName: Full=Nitrous-oxide reductase; EC=1.7.2.4. file:RHOPA/nosZ/nosZ-uniprot.txt PANTHER; PTHR42838:SF2; NITROUS-OXIDE REDUCTASE. file:interpro/panther/PTHR42838/PTHR42838-deep-research-falcon.md PTHR42838 family research separates true NosZ/N2OR proteins from cytochrome c oxidase subunit II homologs and warns against assigning oxidase activity to NosZ from CuA-domain similarity. |
| GO:0005507 copper ion binding | IEA GO_REF:0000120 | ACCEPT | Summary: ACCEPT. Nitrous-oxide reductase is a copper enzyme. Reason: NosZ binds copper cofactors required for nitrous-oxide reduction. UniProt notes six copper cations per subunit and identifies the CuA and CuZ centers. Falcon supports the conserved CuA/CuZ architecture but did not recover Q6N843-specific metal analysis. Supporting Evidence: file:RHOPA/nosZ/nosZ-uniprot.txt Binds 6 Cu cations per subunit. Each subunit contains 2 copper centers, CuA and CuZ. file:RHOPA/nosZ/nosZ-deep-research-falcon.md Canonical NosZ enzymes contain CuA electron-entry and CuZ catalytic copper centers for N2O reduction; Q6N843-specific metal analysis was not recovered. |
| GO:0005509 calcium ion binding | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: KEEP_AS_NON_CORE. This may reflect family-level cofactor information, but copper-dependent nitrous-oxide reduction is the core molecular function. Reason: Calcium binding may be associated with the family/domain model, but the core experimentally meaningful cofactor for NosZ catalysis is copper. Keep as non-core rather than centering the review on this cofactor. Supporting Evidence: file:RHOPA/nosZ/nosZ-uniprot.txt Binds 2 calcium ions per subunit. |
| GO:0016020 membrane | IEA GO_REF:0000120 | UNDECIDED | Summary: UNDECIDED. NosZ is usually exported to the periplasm and can associate with membrane electron-transfer systems, but this broad membrane annotation is not resolved from the current automated evidence alone. Reason: The protein is predicted to be exported to the periplasm by the Tat system. A broad membrane annotation may reflect associated respiratory electron-transfer context or family transfer rather than the location of the soluble catalytic protein itself, so this is left unresolved. Falcon supports periplasmic/Tat biology as family-level evidence but did not find a CGA009 localization experiment. Supporting Evidence: file:RHOPA/nosZ/nosZ-uniprot.txt SUBCELLULAR LOCATION: Periplasm. file:RHOPA/nosZ/nosZ-uniprot.txt Predicted to be exported by the Tat system. file:RHOPA/nosZ/nosZ-deep-research-falcon.md NosZ is commonly Tat-exported to the periplasm for copper-center maturation, but no Q6N843-specific fractionation experiment was recovered. |
| GO:0042597 periplasmic space | IEA GO_REF:0000120 | ACCEPT | Summary: ACCEPT. Bacterial NosZ functions as an exported/periplasmic denitrification enzyme. Reason: Periplasmic localization is directly predicted in UniProt and is consistent with Tat export of bacterial NosZ nitrous-oxide reductases. Falcon supports this as canonical NosZ-family biology rather than direct CGA009 localization evidence. Supporting Evidence: file:RHOPA/nosZ/nosZ-uniprot.txt SUBCELLULAR LOCATION: Periplasm. file:RHOPA/nosZ/nosZ-deep-research-falcon.md NosZ family literature supports periplasmic maturation after Tat export; Q6N843-specific localization was not directly resolved. |
| GO:0050304 nitrous-oxide reductase activity | IEA GO_REF:0000120 | ACCEPT | Summary: ACCEPT. This is the specific molecular function of NosZ. Reason: This is the precise EC-supported activity for the protein. UniProt names the sequence nitrous-oxide reductase, assigns EC 1.7.2.4, and PANTHER places it in a nitrous-oxide reductase subfamily. Falcon did not recover a purified R. palustris Q6N843 assay, so the support is EC/subfamily/family mechanism. Supporting Evidence: file:RHOPA/nosZ/nosZ-uniprot.txt RecName: Full=Nitrous-oxide reductase; EC=1.7.2.4. file:RHOPA/nosZ/nosZ-deep-research-falcon.md NosZ-family literature supports N2O + 2 electrons + 2 protons to N2 and water as the core reaction; no Q6N843-specific kinetic assay was recovered. |
| GO:1902600 proton transmembrane transport | IEA GO_REF:0000108 | UNDECIDED | Summary: UNDECIDED. The gene participates in respiratory electron transfer, but direct assignment of proton transmembrane transport to NosZ itself is not supported by the current local evidence. Reason: NosZ is part of a respiratory chain at the pathway level, but the local evidence identifies this gene product as nitrous-oxide reductase rather than a proton-translocating complex. Do not infer direct proton transport from respiratory-chain participation alone. Supporting Evidence: file:RHOPA/nosZ/nosZ-uniprot.txt Nitrous-oxide reductase is part of a bacterial respiratory chain that uses nitrate or nitrous oxide. |
| GO:0019333 denitrification pathway | IEA GO_REF:0000041 | ACCEPT | Summary: ACCEPT. UniPathway correctly captures the pathway role of NosZ as the terminal nitrous-oxide-reduction enzyme in denitrification. Reason: The denitrification pathway annotation follows directly from the enzyme role: NosZ catalyzes nitrous oxide reduction, the terminal step in denitrification. This is supported by conserved NosZ family/EC evidence and UniProt pathway mapping. Falcon supports the terminal N2O-sink step and notes that electron delivery/accessory requirements are context dependent. Supporting Evidence: file:RHOPA/nosZ/nosZ-uniprot.txt PATHWAY: Nitrogen metabolism; nitrate reduction (denitrification); dinitrogen from nitrate: step 4/4. file:interpro/panther/PTHR42838/PTHR42838-deep-research-falcon.md NosZ/N2OR catalyzes N2O reduction to N2, the terminal step of denitrification, while cytochrome c oxidase subunit II is a distinct CuA-containing electron-entry subunit. file:RHOPA/nosZ/nosZ-deep-research-falcon.md NosZ is the only known biological N2O sink and the terminal respiratory reductase for N2O-to-N2 conversion; gene-neighborhood and regulation details for Q6N843 were not directly resolved. |
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