Structural impact of proline mutations in the loop region of an ancestral membrane protein
Bibliographic record
Abstract
The sodium ion-translocating F0 F1 ATP synthase from the bacterium Ilyobacter tartaricus contains a highly stable rotor ring composed of 11 c subunits. The synthase subunit c-in effect an 89-residue peptide that folds into a helical hairpin consisting of two membrane-spanning helices and a cytoplasmic loop-was probed for the structural impact of a series of substitutions with the β-turn-inducing proline-glycine couplet scanning the hairpin loop (residues 44-51) of the I. tartaricus sequence. We found that a Pro residue in other than the wild type position 47 alters the gross secondary structure of subunit c from α-helical to β-sheet-like, as well as changing its oligomeric ring structure, and its stability toward heat and trichloroacetic acid treatment. Such a Pro-mediated structural switch in one of the first membrane proteins in life hints to a potential evolutionary connection between α-helical and β-sheet membrane proteins.
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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".