Is there nascent structure in the intrinsically disordered region of troponin I?
Bibliographic record
Abstract
In striated muscle, the binding of calcium to troponin C (TnC) results in the removal of the C-terminal region of the inhibitory protein troponin I (TnI) from actin. While structural studies of the muscle system have been successful in determining the overall organization of most of the components involved in force generation at the atomic level, the structure and dynamics of the C-terminal region of TnI remains controversial. This domain of TnI is highly flexible, and it has been proposed that this intrinsically disordered region (IDR) regulates contraction via a "fly-casting" mechanism. Different structures have been presented for this region using different methodologies: a single α-helix, a "mobile domain" containing a small β-sheet, an unstructured region, and a two helix segment. To investigate whether this IDR has in fact any nascent structure, we have constructed a skeletal TnC-TnI chimera that contains the N-domain of TnC (1-90), a short linker (GGAGG), and the C-terminal region of TnI (97-182) and have acquired ¹⁵N NMR relaxation data for this chimera. We compare the experimental relaxation parameters with those calculated from molecular dynamic simulations using four models based upon the structural studies. Our experimental results suggest that the C-terminal region of TnI does not contain any defined secondary structure, supporting the "fly-casting" mechanism. We interpret the presence of a "plateau" in the ¹⁵N NMR relaxation data as being an intrinsic property of IDRs. We also identified a more rigid adjacent region of TnI that has implications for muscle performance under ischemic conditions.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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".