The C-terminal Domain of the Escherichia coli WaaJ Glycosyltransferase Is Important for Catalytic Activity and Membrane Association
Bibliographic record
Abstract
The waaJ gene encodes an alpha-1,2-glucosyltransferase involved in the synthesis of the outer core region of the lipopolysaccha-ride of some Escherichia coli and Salmonella isolates. WaaJ belongs to glycosyltransferase CAZy family 8, characterized by the GT-A fold, a DXD motif, and by retention of configuration at the anomeric carbon of the donor sugar. Detailed kinetic and structural information for bacterial family 8 glycosyltransferases has resulted from studies of Neisseria meningitidis LgtC. As many as 28 amino acids could be deleted from the C terminus of LgtC without affecting its in vitro catalytic behavior. This C-terminal domain has a high ratio of positively charged and hydrophobic residues, a feature conserved in WaaJ and some other family 8 representatives. Unexpectedly, deletion of as few as five residues from the C terminus of WaaJ resulted in substantially reduced in vivo activity. With deletions of 15 residues or less, activity was only detected when levels of expression were elevated. No in vivo activity was detected after the removal of 20 amino acids, regardless of expression levels. Longer deletions (20 residues and greater) compromised the ability of WaaJ to associate with the membrane. However, the reduced in vivo activity in enzymes lacking 5-12 C-terminal residues also reflected a dramatic drop in catalytic activity in vitro (a 294-fold decrease in the apparent kcat/Km,LPS). Deletions removing 20 or more residues resulted in a protein showing no detectable in vitro activity. Therefore, the C-terminal domain of WaaJ plays a critical role in enzyme function.
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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 | 0.001 |
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".