The <i>Escherichia coli</i> Enterotoxin STb Permeabilizes Piglet Jejunal Brush Border Membrane Vesicles
Bibliographic record
Abstract
The membrane-permeabilizing ability of the Escherichia coli enterotoxin STb was evaluated using brush border membrane vesicles isolated from piglet jejunum and a membrane-potential-sensitive fluorescent probe, 3,3'-dipropylthiadicarbocyanine iodide. A strong membrane potential was generated by the efflux of K+ ions from the vesicles in the presence of the potassium ionophore valinomycin. Under these conditions, preincubation of the vesicles with STb efficiently depolarized the membrane in a dose-dependent and saturable manner. This activity was independent of pH, however, at least between pH 5.5 and 8.0. On the other hand, in the absence of valinomycin, STb had no significant influence on the measured fluorescence levels, indicating that it was unable to modify the ionic selectivity of the intact membrane. In agreement with the fact that the integrity of the disulfide bridges of STb is known to be essential for its biological activity, a reduced and alkylated form of the toxin was unable to depolarize the membrane in the presence of valinomycin. Furthermore, two previously described poorly active STb mutants, M42S and K22A-K23A, showed no membrane-permeabilizing capacity. These results demonstrate for the first time that STb can permeabilize its target membrane and suggest that it does so by forming nonspecific pores.
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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".