| Category | Finding for **Ferroglobus placidus** Ferp_0128 / UniProt **D3S180** | Evidence / citation |
|---|---|---|
| Identifier verification | **Ferp_0128** maps to a predicted **nitrous-oxide reductase (NosZ)** in **Ferroglobus placidus strain DSM 10642 / AEDII12DO**; this matches the organism and locus context used in the F. placidus literature. | Smith et al. studied **F. placidus strain AEDII12DO (DSM 10642)** and explicitly refer to **nosZ; Ferp_0128** in this organism (pqac-00000006, pqac-00000008) |
| Predicted primary function | Predicted enzyme: **nitrous-oxide reductase / N2O reductase (NosZ)**, the terminal enzyme of denitrification that reduces **N2O to N2**; UniProt assigns **EC 1.7.2.4**. | General denitrification role of NosZ in prokaryotes and archaea is reviewed in archaeal nitrogen-cycle literature (pqac-00000003); large genome-based denitrification resource also lists **nosZ = nitrous-oxide reductase** (pqac-00000002) |
| Reaction / substrate specificity | Expected catalytic reaction: **N2O + 2 e− + 2 H+ → N2 + H2O**; substrate specificity is **nitrous oxide** as terminal electron acceptor. | NosZ is the enzyme responsible for **microbial nitrous oxide reduction to nitrogen gas** in denitrification (pqac-00000003, pqac-00000000) |
| Protein family / domains | Functional annotation is consistent with a canonical/atypical **NosZ multicopper oxidoreductase** architecture, including **N2OR N/C regions** and **cupredoxin-related domains**; Jones et al. note that the **F. placidus nosZ** belongs to the broad **clade II** lineage, and Smith et al. note the nitrous-oxide reductase operon product **contains a cupredoxin domain**. | nosZ phylogeny and clade assignment discussed for **F. placidus** in Jones et al. (pqac-00000001); Smith et al. mention the nitrous oxide reductase operon product “also contains a cupredoxin domain” (pqac-00000008) |
| Export / localization evidence | NosZ proteins are generally **extracytoplasmic/periplasm-facing** enzymes. For most **clade II nosZ**, Jones et al. found a **Sec signal recognition motif**, but they specifically note **Ferroglobus placidus is an exception**, so the export route for Ferp_0128 is **not securely assigned from that survey alone**. | Clade II nosZ usually encoded a **Sec signal motif**, “with the exception of … **Ferroglobus placidus**” (pqac-00000001); general NosZ localization in archaea/prokaryotes is periplasmic/extracytoplasmic (pqac-00000003, pqac-00000000) |
| Physiological pathway context | Ferp_0128 most plausibly functions in **N2O reduction / denitrification** and therefore could contribute to an **N2O sink** phenotype, even if the organism lacks evidence here for a fully conventional denitrification chain in the cited sources. | NosZ marks the **nitrous oxide reduction trait** in comparative genome analyses (pqac-00000002); Jones et al. frame noncanonical/clade II nosZ organisms as part of an underappreciated N2O-reducing community (pqac-00000001) |
| Archaeal context | Archaeal **nosZ** genes are sufficiently conserved that archaeal-specific nosZ primers were designed and experimentally validated using archaeal references that include **F. placidus**. | Rusch 2013 reports archaeal nosZ primer design/evaluation and includes archaeal nosZ references including **F. placidus** (pqac-00000007) |
| Relationship to Fe(III) respiration study | In the major **F. placidus** Fe(III)-respiration transcriptomics study, Ferp_0128 is discussed only indirectly in the context of neighboring redox genes; there is **no direct evidence** from that study that NosZ is a Fe(III)-reduction protein. | Smith et al. focused on Fe(III) respiration mechanisms and c-type cytochromes rather than validating NosZ biochemistry in F. placidus (pqac-00000006, pqac-00000004, pqac-00000005) |
| Expression / regulation in Smith 2015 | **Ferp_0128 (nosZ) was not differentially regulated** between growth on **Fe(III) oxide** and **Fe(III) citrate**. However, a nearby **cupredoxin superfamily gene, Ferp_0125**, divergently transcribed from the nitrous-oxide reductase operon, **was upregulated** during growth on Fe(III) oxide. | Smith et al. explicitly state **“nitrous oxide reductase (nosZ; Ferp_0128) was not differentially regulated”** and that nearby **Ferp_0125** was upregulated (pqac-00000008) |
| Strength of evidence | **Moderate-confidence functional inference, limited gene-specific experimentation.** Identity is supported by organism/locus mapping and comparative NosZ biology, but direct biochemical characterization of **Ferp_0128** itself in **F. placidus** appears limited in the retrieved literature. | Combined organism-specific and comparative evidence (pqac-00000001, pqac-00000003, pqac-00000006, pqac-00000008) |
| Key source URLs / dates | Smith et al., *Applied and Environmental Microbiology* (2015-04), DOI: https://doi.org/10.1128/AEM.04038-14 ; Jones et al., *ISME Journal* (2013-02 issue; online 2012-11), DOI: https://doi.org/10.1038/ismej.2012.125 ; Cabello et al., *Microbiology* (2004-11), DOI: https://doi.org/10.1099/mic.0.27303-0 ; Rusch, *Archaea* (2013-01), DOI: https://doi.org/10.1155/2013/676450 ; Isokpehi et al., *Microorganisms* (2024-04), DOI: https://doi.org/10.3390/microorganisms12040791 | Source metadata from retrieved papers (pqac-00000001, pqac-00000002, pqac-00000003, pqac-00000006, pqac-00000007, pqac-00000008) |


*Table: This table summarizes the verified identity, predicted function, domain architecture, localization evidence, physiological context, and expression data for Ferroglobus placidus Ferp_0128 (UniProt D3S180). It emphasizes where evidence is direct versus inferred from broader NosZ biology.*