Expression of the ExeAB complex of <i>Aeromonas hydrophila</i> is required for the localization and assembly of the ExeD secretion port multimer
Bibliographic record
Abstract
Aeromonas hydrophila secretes protein toxins via the type II pathway, involving the products of at least two operons, exeAB (gspAB) and exeC-N (gspC-N). In the studies reported here, aerolysin secretion was restored to C5.84, an exeA::Tn5-751 mutant, by overexpression of exeD alone in trans. Expression studies indicated that these results did not reflect a role of ExeAB in the regulation of the exeC-N operon. Instead, immunoblot analysis showed that ExeD did not multimerize in C5.84, and fractionation of the membranes showed that the monomeric ExeD remained in the inner membrane. Expression of ExeAB, but not either protein alone, from a plasmid in C5.84 resulted in increases in the amount of multimeric ExeD, which correlated with increases in aerolysin secretion. Pulse-chase analysis also suggested that the induction of ExeAB allowed multimerization of previously accumulated monomer ExeD. In C5.84 cells overproducing ExeD, it multimerized even in the absence of ExeAB and, although most remained in the inner membrane, an amount similar to that in wild-type outer membranes fractionated with the outer membrane of the overproducing cells. These results indicate that the secretion defect of exeAB mutants is a result of an inability to assemble the ExeD secretin in the outer membrane. The localization and multimerization of overproduced ExeD in these mutants further suggests that the ExeAB complex plays either a direct or indirect role in the transport of ExeD into the outer membrane.
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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) | 0.000 | 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 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".