Solution Structure of Escherichia coli FeoA and Its Potential Role in Bacterial Ferrous Iron Transport
Bibliographic record
Abstract
Iron is an indispensable nutrient for most organisms. Ferric iron (Fe(3+)) predominates under aerobic conditions, while during oxygen limitation ferrous (Fe(2+)) iron is usually present. The Feo system is a bacterial ferrous iron transport system first discovered in Escherichia coli K-12. It consists of three genes, feoA, feoB, and feoC (yhgG). FeoB is thought to be the main transmembrane transporter while FeoC is considered to be a transcriptional regulator. Using multidimensional nuclear magnetic resonance (NMR) spectroscopy, we have determined the solution structure of E. coli FeoA. The structure of FeoA reveals a Src-homology 3 (SH3)-like fold. The structure is composed of a β-barrel with two α-helices where one helix is positioned over the barrel. In comparison to the standard eukaryotic SH3 fold, FeoA has two additional α-helices. FeoA was further characterized by heteronuclear NMR dynamics measurements, which suggest that it is a monomeric, stable globular protein. Model-free analysis of the NMR relaxation results indicates that a slow conformational dynamic process is occurring in β-strand 4 that may be important for function. (31)P NMR-based GTPase activity measurements with the N-terminal domain of FeoB (NFeoB) indicate a higher GTP hydrolysis rate in the presence of potassium than with sodium. Further enzymatic assays with NFeoB suggest that FeoA may not act as a GTPase-activating protein as previously proposed. These findings, together with bioinformatics and structural analyses, suggest that FeoA may have a different role, possibly interacting with the cytoplasmic domain of the highly conserved core portion of the FeoB transmembrane region.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".