Role of residues on the proximal side of the heme in catalase HPII of Escherichia coli
Bibliographic record
Abstract
Through site-directed mutagenesism the roles of the amino acids H392, H395, D197, Q419 in heme conversion were studied. H392 mutants which disable the His-Tyr bond contain only heme b as their prosthetic group, and lose specific activity, thermostability and sensitivity to the inhibitors NaCN, NaN3, NH2OH, CH3ONH2, C2 H5ONH2 compared to wild type HPII. Populations of D197S/H395Q and 0419A mutant HPII contain both heme b and heme d as their prosthetic group, and are less thermostable compared to wild type HPII but retain wild type HPII characteristics regarding enzyme kinetics and inhibitor sensitivity. H395A, H395Q, D 97A, D197S and Q419H mutants showed no significant differences when compared to wild type HPII. It therefore appears that, while His392, His395, Asp 197 and Gln419 are all involved in heme conversion, only the presence of His392 is absolutely critical for the reaction to proceed. These results support the mechanistic relationship between the proposed autocatalytic conversion of heme b to heme d mechanism proposed by Bravo 'et al'. (1997a). (Abstract shortened by UMI.)
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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) | 0.001 | 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".