Identification of Two Structural Elements Important for Ribosome-Dependent GTPase Activity of Elongation Factor 4 (EF4/LepA)
Bibliographic record
Abstract
The bacterial translational GTPase EF4/LepA is structurally similar to the canonical elongation factor EF-G. While sharing core structural features with other translational GTPases, the function of EF4 remains unknown. Recent structural data locates the unique C-terminal domain (CTD) of EF4 in proximity to the ribosomal peptidyl transferase center (PTC). To investigate the functional role of EF4's CTD we have constructed three C-terminal truncation variants. These variants are fully functional with respect to binding mant-GTP and mant-GDP as determined by rapid kinetics, as well as their intrinsic multiple turnover GTPase activity. Furthermore, they are able to form stable complexes with the 70S ribosome and 50S/30S ribosomal subunits. However, successive removal of the C-terminus impairs ribosome-dependent multiple turnover GTPase activity of EF4, which for the full-length protein is very similar to EF-G. Our findings suggest that the last 44 C-terminal amino acids of EF4 form a sub-domain within the C-terminal domain that is important for GTP-dependent function on the ribosome. Additionally, we show that efficient nucleotide hydrolysis by EF4 on the ribosome depends on a conserved histidine (His 81), similar to EF-G and EF-Tu.
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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".