Entry exclusion in F-like plasmids requires intact TraG in the donor that recognizes its cognate TraS in the recipient
Bibliographic record
Abstract
The mating pair stabilization (Mps) protein of the F plasmid, TraG, is unique to F-like type IV secretion systems. TraG is a polytopic inner-membrane protein with a large C-terminal periplasmic domain that is required for piliation and Mps, whereas the N-terminal region is sufficient for pilus synthesis. The C-terminal region of TraG is thought to be cleaved by the host signal peptidase I to give a fragment called TraG* that is responsible for Mps. Using mutational analysis and cell localization studies, it was shown that TraG* is most probably an artifact caused by non-specific degradation. TraS (173 aa in F), which is involved in entry exclusion (Eex), blocks redundant conjugative DNA synthesis and transport between donor cells, suggesting that it interferes with a signalling pathway required to trigger DNA transfer. Using the F and R100 plasmids, TraG in the donor cell was found to recognize TraS in the recipient cell inner membrane, in a plasmid-specific manner. This activity mapped to aa 610-673 in F TraG, the only region that differs significantly from R100 TraG. Expression of traG or traG* in a recipient cell did not affect mating ability or Eex. These results suggest that TraG may be translocated to the recipient cell, where it contacts the inner membrane, initiating transfer, a process that is blocked by TraS.
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How this classification was reachedexpand
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 | 0.001 | 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 | 0.001 | 0.000 |
| Research integrity | 0.001 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".