Structure of<i>Staphylococcus aureus</i>5′-methylthioadenosine/<i>S</i>-adenosylhomocysteine nucleosidase
Bibliographic record
Abstract
5'-Methylthioadenosine/S-adenosylhomocysteine nucleosidase (MTAN) catalyzes the irreversible cleavage of the glycosidic bond in 5'-methylthioadenosine (MTA) and S-adenosylhomocysteine (SAH) and plays a key role in four metabolic processes: biological methylation, polyamine biosynthesis, methionine recycling and bacterial quorum sensing. The absence of the nucleosidase in mammalian species has implicated this enzyme as a target for antimicrobial drug design. MTAN from the pathogenic bacterium Staphylococcus aureus (SaMTAN) has been kinetically characterized and its structure has been determined in complex with the transition-state analogue formycin A (FMA) at 1.7 A resolution. A comparison of the SaMTAN-FMA complex with available Escherichia coli MTAN structures shows strong conservation of the overall structure and in particular of the active site. The presence of an extra water molecule, which forms a hydrogen bond to the O4' atom of formycin A in the active site of SaMTAN, produces electron withdrawal from the ribosyl group and may explain the lower catalytic efficiency that SaMTAN exhibits when metabolizing MTA and SAH relative to the E. coli enzyme. The implications of this structure for broad-based antibiotic design are discussed.
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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 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".