Properties of the major non-specific endonuclease from the strict anaerobe Fibrobacter succinogenes and evidence for disulfide bond formation in vivo
Bibliographic record
Abstract
DNase A is a non-specific endonuclease of Fibrobacter succinogenes. The enzyme was purified to homogeneity and its properties studied both in vitro and in vivo. Magnesium but not calcium was essential for nucleolytic activity. Manganese ions substituted for magnesium but were less stimulatory. DNase A activity was markedly inhibited by either NaCl or KCl at concentrations greater than 75 mM. The enzyme had a temperature optimum of 25 degrees C and a pH optimum of about 7.0. Values for K:(m) and K:(cat) were determined to be 61 microM and 330 s(-1) respectively, with a catalytic efficiency approximately threefold greater than bovine pancreatic DNase I, but 10-fold less than the Serratia marcescens NucA. DNase A was localized to the periplasm and probably exists as a monomeric species. The enzyme possessed one or more disulfide bonds. In the reduced form it had an apparent mass of 33 kDa, while in the oxidized form it was 29 kDa as estimated by SDS-PAGE. Reduction of the disulfide bonds by dithiothreitol with or without subsequent alkylation by iodoacetamide strongly inactivated the enzyme. DNase A accumulated in vivo had an apparent mass of 29 kDa, indicating that it was in an oxidized form. This is the first indication in a strict anaerobe of a functional periplasmic disulfide bond forming system, phenotypically similar to Dsb systems in facultative and aerobic bacteria.
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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) | 0.001 | 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".