Regulation of transcription by the activity of the <i>Shigella flexneri</i> type III secretion apparatus
Bibliographic record
Abstract
The virulence plasmid-encoded type III secretion system of Shigella flexneri consists of the Mxi-Spa secretion apparatus, secreted proteins IpaA-D and IpgD involved in entry of bacteria into epithelial cells,cytoplasmic chaperones IpgC and IpgE and 15 other secreted proteins of unknown function, including VirA and members of the IpaH family. The activity of the Mxi-Spa apparatus is regulated by external signals, and transcription of virA and IpaH genes is specifically induced in conditions of active secretion. We present genetic evidence that regulation of these genes involves both MxiE, the transcriptional activator of the AraC family encoded by the mxi operon, and IpgC, the chaperone for IpaB and IpaC. We also show that together MxiE and IpgC are sufficient to activatevirA and IpaH 9.8 promoters in Escherichia coli. InS. flexneri, increasing the expression of IpgC led to a concomitant increase in IpaH production in conditions of non-secretion. This suggests that the activity of secretion is sensed by the presence of free IpgC, which acts as a coactivator to allow MxiE to activate transcription at its target promoters.
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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".