| Claim/feature | Evidence type | Key details | Source (first author year) | DOI/URL |
|---|---|---|---|---|
| Gene identity and locus context | C. necator direct | UniProt Q9K4U8 corresponds to norR2 / H16_B2325 in *Cupriavidus necator* H16. In the denitrification dataset, chromosome 2 carries a norR2A2B2 locus; H16_B2323 = norB2 and H16_B2324 = norA2, with NOR2 located in the chromosome-2 denitrification hot spot / region III. This supports assignment of H16_B2325 as the upstream regulator for the NOR2 operon (pqac-00000002, pqac-00000006). | Kohlmann 2014 | https://doi.org/10.1021/pr500491r |
| Domain architecture | Mixed: C. necator direct for NorR assignment; other-species general for detailed domain model | NorR in *R. eutropha/C. necator* is described as an NtrC-like, sigma54-dependent enhancer-binding regulator with N-terminal GAF, central AAA+ ATPase, and C-terminal DNA-binding domain architecture; this matches the domain annotation supplied for Q9K4U8 (pqac-00000000, pqac-00000001). | Zumft 2008; Cadby 2014 | https://doi.org/10.1016/b978-044452839-1.50014-0 |
| Mechanism of action | Mixed: C. necator direct for sigma54 / NorR-linked regulation; other-species general for sensing chemistry | In *R. eutropha/C. necator*, NorR activates sigma54-dependent norA-linked promoters and recognizes enhancer-like partially palindromic sites with consensus GGT-(N7)-ACC (pqac-00000000). Detailed biochemical mechanism is from *E. coli* NorR: the GAF domain binds a mononuclear non-heme Fe center that forms an {Fe(NO)}7 mononitrosyl upon NO binding, which activates the AAA+ ATPase to drive open-complex formation by sigma54-RNA polymerase (pqac-00000000, pqac-00000001). | Zumft 2008; Cadby 2014 | https://doi.org/10.1016/b978-044452839-1.50014-0 |
| Regulatory targets | C. necator direct | The direct target is the norA2B2 promoter / operon on chromosome 2, part of the two functional NOR systems norR1A1B1 on pHG1 and norR2A2B2 on chromosome 2. Under denitrifying conditions, NOR2 genes are strongly induced: norB2 (H16_B2323) reported around log2 7.2-7.3 and 6.3-6.6 in dataset comparisons; norA2 (H16_B2324) around log2 7.8, 7.3, 7.1, 6.3, 4.8, and 5.4 across transcript / protein contrasts, consistent with NO-responsive NorR activation (pqac-00000002, pqac-00000003). | Kohlmann 2014 | https://doi.org/10.1021/pr500491r |
| Subcellular localization inference | Mixed: C. necator direct for NOR subunits; inferred for NorR2 | NorR2 is most plausibly a soluble cytosolic DNA-binding transcription regulator acting on chromosome 2 promoters; no direct localization experiment for NorR2 was reported in the gathered evidence (pqac-00000001). For its regulated enzyme system, NorB1 / NorB2 were 20-30-fold more abundant in membrane fractions than soluble fractions, while NorA1 / NorA2, though considered soluble NO-binding partners, were also detected in membrane fractions, plausibly to bind hydrophobic NO near the membrane (pqac-00000003). | Cadby 2014; Kohlmann 2014 | https://doi.org/10.1021/pr500491r |
| Quantitative denitrification dataset statistics | C. necator direct | Combined proteomics / transcriptomics identified 2261 proteins, about 34 percent of the genome. Using p less than or equal to 0.05 and at least 4-fold change cutoffs, 324 proteins were differentially expressed: 174 enriched aerobically and 150 under oxygen deficiency; 20 and 55 proteins reached up to 16-fold overexpression in aerobic and anaerobic conditions, respectively. The denitrification regulator DnrD was strongly induced at T|SP-D: 32-fold (pqac-00000004, pqac-00000005). | Kohlmann 2014 | https://doi.org/10.1021/pr500491r |


*Table: This table summarizes the strongest gathered evidence for functional annotation of *Cupriavidus necator* H16 norR2 (Q9K4U8/H16_B2325), separating direct organism-specific findings from inferences based on NorR-family studies in other bacteria. It is useful for distinguishing what is experimentally supported in *C. necator* from what is inferred from conserved NorR mechanism.*