Unveiling the <scp>GT114</scp> family: Structural characterization of <scp>A075L</scp>, a glycosyltransferase from <i>Paramecium bursaria</i> chlorella virus‐1 (<scp>PBCV</scp>‐1)
Bibliographic record
Abstract
Abstract Protein A075L is a β‐xylosyltransferase that participates in producing the core of the N‐glycans found in VP54, the major viral capsid protein of Paramecium bursaria chlorella virus‐1 (PBCV‐1). In this study, we present an X‐ray crystallographic analysis of the apo form of A075L, along with its complexes with the sugar donor and with a trisaccharide acceptor. The protein structure shows a typical GT‐B folding, with two Rossmann‐like fold domains, in which the acceptor substrate binds to the N‐terminal region, and the nucleotide‐sugar donor binds to the C‐terminal region. We propose that the catalytic mechanism follows a direct displacement S N 2‐like reaction, where Asp73 serves as a catalytic base that deprotonates the incoming nucleophile of the acceptor, facilitating direct displacement of the UDP with the inversion of the anomeric configuration of the acceptor without metal ion dependence, while the interactions with side chains of Arg158 and Arg208 stabilize the developing negative charge. Using isothermal titration calorimetry, nuclear magnetic resonance spectroscopy, high‐performance liquid chromatography, and molecular dynamics simulations, the catalytic activity and specificity of this enzyme have been unraveled.
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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) | 0.000 | 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 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".