Selective labeling supports 5-thiooxazole post-translational modification in bufferins
Bibliographic record
Abstract
Abstract Multinuclear nonheme iron-dependent oxidases (MNIOs) constitute one of the largest families of enzymes involved in natural product biosynthesis. Distinct MNIO subfamilies utilize molecular oxygen to catalyze a wide variety of complex peptide rearrangements, including β-carbon excision and heterocyclization. Highly homologous MNIOs have been proposed to install either oxazolone-thioamides or 5-thiooxazoles as cysteine post-translational modifications in the closely related bufferin and EGKCG families of peptide chalkophores. These alternative structures prompted discussion of the subtle mechanistic features of MNIO enzymes that might determine reaction outcome. Here, we combine uniform 15N labeling with cysteine-specific carbonyl 13C labeling to unambiguously assign 5-thiooxazoles as the cysteine modifications in bufferins. Together with the recent identification of 5-thiooxazoles in three members of the sister EGKCG family and the re-assignment of the cysteine modification in oxazolin, these findings confirm that closely related MNIOs catalyze identical post-translational modifications.
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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".