Crystal Structure of the Salmonella Typhimurium Effector GtgE
Bibliographic record
Abstract
Salmonella Typhimurium GtgE is an effector protein contributing to the virulence of this pathogen. It was shown to possess highly selective proteolytic activity against a subset of Rab proteins that helps in evasion of Salmonella-containing vacuole (SCV) fusion with lysosomes. Cys45, His151 and Asp169 are essential for proteolytic activity. The structure of a C-terminal fragment GtgE(79-214) indicated the presence of a papain-like fold. Here, we present the structure of GtgE(17-214) containing the fully assembled active site. The design of a proteolytically active and crystallizable GtgE construct was aided by NMR spectroscopy. The protein indeed displays papain-like fold with an assembled Cys-His-Asp catalytic triad. Like the full-length GtgE, the crystallizable construct showed low activity in vitro for its known substrates, Rab32 and Rab29. NMR titration experiments showed at most very weak binding of GtgE to the peptide encompassing the Rab29 cleavage site. In view of the low in vitro activity and poor substrate binding, we postulate that the function of GtgE in vivo as a proteolytic enzyme is dependent on other factor(s), such as a protein partner or interactions with the SCV membrane, which stimulate(s) GtgE activity in vivo.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.005 | 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".