Mismatch Uracil Glycosylase from Escherichia coli
Bibliographic record
Abstract
The gene for the mismatch-specific uracil glycosylase (MUG) was identified in the Escherichia coli genome as a sequence homolog of the mammalian thymine DNA glycosylase, with activity against uracil in U.G mismatches. Subsequently, 3,N4-ethenocytosine (epsilonC), thymine, 5-hydroxymethyluracil, and 8-(hydroxymethyl)-3,N4-ethenocytosine have been proposed as possible substrates for this enzyme. The evaluation of various DNA adducts as substrates is complicated by the biphasic nature of the kinetics of this enzyme. Our results demonstrate that product release by the enzyme is very slow and hence comparing the "steady-state" parameters of the enzyme for different substrates is of limited use. Consequently, the ability of the enzyme to excise a variety of damage products of purines and pyrimidines was studied under single turnover conditions. Although the enzyme excised both epsilonC and U from DNA, the former adduct was significantly better as a substrate in terms of binding and hydrolysis. Some products of oxidative and alkylation damage are also moderately good substrates for the enzyme, but thymine is a poor substrate. This comparison of different substrates under single turnover conditions provides a rational basis for comparing substrates of MUG and we relate these conclusions to the known crystal structures of the enzyme and its catalytic mechanism.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.004 |
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".