N-Terminal Modifications Increase the Neutral-pH Stability of Pepsin
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Bibliographic record
Abstract
A structure-function study was undertaken to determine the effects of N-terminal mutations in pepsin designed to introduce the Lys-X-Tyr motif and increase N-terminal flexibility. At pH 7.0, E7K/T12A/E13Q pepsin was inactivated more slowly compared to WT, whereas the mutants E7K and T12A/E13Q were not stabilized. Far-UV circular dichroism revealed that changes in secondary structure accompanied the inactivation process, and that the structural changes occurred at approximately the same rate as inactivation. All of the inactivated pepsin forms showed retention of substantial secondary structure, more than previously determined for pepsin denatured at pH 7.2 and 8.0, suggesting the presence of a structural intermediate at pH 7.0. The coupled mutations at positions 12 and 13 impacted the pH dependence of activity at pH 0.9, lowered affinity for a synthetic substrate, and lowered the turnover number. The introduction of Lys at position 7 apparently destabilized the interaction between prosegment-enzyme body as evidenced by activation at higher pH (>or= 4.0) compared to WT, but showed no change for pH dependence of activity, nor a statistically significant change in affinity for the synthetic substrate.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 it