Structural Model for Phenylalkylamine Binding to L-type Calcium Channels
Bibliographic record
Abstract
Phenylalkylamines (PAAs), a major class of L-type calcium channel (LTCC) blockers, have two aromatic rings connected by a flexible chain with a nitrile substituent. Structural aspects of ligand-channel interactions remain unclear. We have built a KvAP-based model of LTCC and used Monte Carlo energy minimizations to dock devapamil, verapamil, gallopamil, and other PAAs. The PAA-LTCC models have the following common features: (i) the meta-methoxy group in ring A, which is proximal to the nitrile group, accepts an H-bond from a PAA-sensing Tyr_IIIS6; (ii) the meta-methoxy group in ring B accepts an H-bond from a PAA-sensing Tyr_IVS6; (iii) the ammonium group is stabilized at the focus of P-helices; and (iv) the nitrile group binds to a Ca(2+) ion coordinated by the selectivity filter glutamates in repeats III and IV. The latter feature can explain Ca(2+) potentiation of PAA action and the presence of an electronegative atom at a similar position of potent PAA analogs. Tyr substitution of a Thr in IIIS5 is known to enhance action of devapamil and verapamil. Our models predict that the para-methoxy group in ring A of devapamil and verapamil accepts an H-bond from this engineered Tyr. The model explains structure-activity relationships of PAAs, effects of LTCC mutations on PAA potency, data on PAA access to LTCC, and Ca(2+) potentiation of PAA action. Common and class-specific aspects of action of PAAs, dihydropyridines, and benzothiazepines are discussed in view of the repeat interface concept.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.006 | 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".