Repurposing an ancient protein core structure: structural studies on FmtA, a novel esterase of <i>Staphylococcus aureus</i>
Bibliographic record
Abstract
FmtA is a penicillin-recognizing protein (PRP) with novel hydrolytic activity toward the ester bond between D-Ala and the backbone of teichoic acids (TA), the polyol-phosphate polymers found in the S. aureus cell envelope. Two of the PRPs conserved motifs, namely SXXK and Y(S)XN, are involved in this hydrolysis, but its catalytic mechanism remains elusive. Here we determined the crystal structure of FmtA. FmtA shares the core structure of PRPs: an all -helical domain and / domain sandwiched together. However, it does not have the typical PRPs active-site cleft. Its active site is shallow, solvent-exposed and wide. Furthermore, the SXXK and Y(S)XN motifs of FmtA offer all that is necessary for catalysis: the active-site nucleophile (serine) and the general base (lysine) required for acylation and deacylation steps and an anchor (tyrosine) to hold the active-site serine, and possibly the substrate, in an optimum conformation for catalysis [1]. Our study establishes that the FmtA esterase activity represents an expansion of the catalytic activity repertoire of the PRPs core structure, which typically displays peptidase activity. The structure of FmtA provides insights to the design of inhibitor molecules with the potential to serve as leads in the development of novel antibacterial chemotherapeutic agents. Figure 1. Cartoon representation of the FmtA structure with the active-site residues shown in sticks.
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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 | 0.001 |
| 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".