<i>Escherichia coli</i> and <i>Pseudomonas aeruginosa</i> lipopolysaccharide O‐antigen ligases share similar membrane topology and biochemical properties
Bibliographic record
Abstract
WaaL is an inner membrane glycosyltransferase that catalyzes the transfer of O-antigen polysaccharide from its lipid-linked intermediate to a terminal sugar of the lipid A-core oligosaccharide, a conserved step in lipopolysaccharide biosynthesis. Ligation occurs at the periplasmic side of the bacterial cell membrane, suggesting the catalytic region of WaaL faces the periplasm. Establishing the membrane topology of the WaaL protein family will enable understanding its mechanism and exploit it as a potential antimicrobial target. Applying oxidative labeling of native methionine/cysteine residues, we previously validated a topological model for Escherichia coli WaaL, which differs substantially from the reported topology of the Pseudomonas aeruginosa WaaL, derived from the analysis of truncated protein reporter fusions. Here, we examined the topology of intact E. coli and P. aeruginosa WaaL proteins by labeling engineered cysteine residues with the membrane-impermeable sulfhydryl reagent polyethylene glycol maleimide (PEG-Mal). The accessibility of PEG-Mal to targeted engineered cysteine residues in both E. coli and P. aeruginosa WaaL proteins demonstrates that both ligases share similar membrane topology. Further, we also demonstrate that P. aeruginosa WaaL shares similar functional properties with E. coli WaaL and that E. coli WaaL may adopt a functional dimer conformation.
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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 | 0.001 | 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".