Unique Ligand−Protein Interactions in a New Truncated Hemoglobin from <i>Mycobacterium tuberculosis</i>
Bibliographic record
Abstract
A new truncated hemoglobin (HbO) from Mycobacterium tuberculosis has been expressed and purified. Sequence alignment of HbO with other hemoglobins suggests that the proximal F8 residue is histidine and the distal E7 and the B10 positions are occupied by alanine and tyrosine, respectively. The highly conserved residue at the CD1 position, surprisingly, is tyrosine, making HbO the first exception in the hemoglobin family that does not contain phenylalanine at this position. Resonance Raman data suggest that a strong hydrogen bonding network, involving the B10 Tyr and the CD1 Tyr, stabilizes the heme-bound O2 and CO as evidenced by the relatively low frequency of the Fe-O2 stretching mode (559 cm(-1)) and the high frequency of the Fe-CO stretching mode (527 cm(-1)). The presence of this hydrogen bonding network is supported by mutagenesis studies with the B10 tyrosine or the CD1 tyrosine mutated to phenylalanine. Taken together, these data demonstrate a rigid and polar distal pocket in HbO, which is significantly different from that of HbN, the other hemoglobin from M. tuberculosis. The distinct features in the heme active site structures and the temporal expression patterns of HbO and HbN suggest that these two hemoglobins may have very different physiological functions.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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 source (direct Gemma or distilled Codex), 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".