Protoporphyrin IX and heme binding properties of <i>Staphylococcus aureus</i> IsdC
Bibliographic record
Abstract
Staphylococcus aureus is a human pathogen that results in numerous infections in hospital settings and recently also in the wider community. Its antibiotic resistant forms are causing considerable alarm. A series of surface-anchored proteins that have heme uptake and transport properties have been reported. Through the use of absorption and magnetic circular dichroism spectroscopies and mass spectrometry, the iron-free, protoporphyrin IX and the iron-containing, heme-binding characteristics of bacterial rIsdC have been obtained. Mass spectrometry showed that following isolation and purification, the rIsdC is bound predominantly to protoporphyrin IX and to a lesser extent heme, unlike the case of rIsdA, which binds predominantly heme. Magnetic circular dichroism analysis provided further information regarding porphyrin binding because the characteristic magnetic circular dichroism band envelopes for the iron-free protoporphyrin IX and the iron-containing heme can be clearly distinguished in the spectrum of the rIsdC. Analysis of these spectral data showed that the minor heme component exists as a high-intermediate spin state ferric heme when bound to rIsdC, similar to the high-spin ferric heme reported for the rIsdA protein.
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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".