An extended structure of the intracellular domain of the Torpedo nicotinic acetylcholine receptor and its proposed interactions with rapsyn
Bibliographic record
Abstract
Abstract To gain insight into the interactions between rapsyn and the nAChR that induce clustering at the post-synaptic membrane, we refined a cryo-EM dataset using an intracellular domain focused strategy to obtain a 3.0 Å map with the most extensive density yet for the intracellular domain of the Torpedo nAChR. The improved map allowed us to extend the structure beyond the MX α-helix and prior to the MA α-helix of the intracellular domain. The new structure defines a sharp N-terminal boundary of each MA α-helix to place agrin-dependent phosphorylated tyrosines unambiguously within the flexible regions of the MX-MA loops. Two distinct conformations of the α δ M4 α-helix were also resolved, indicating that M4 conformational heterogeneity reflects intrinsic flexibility rather than a change in gating state. The new structural constraints defined for the MX-MA loop were then used to evaluate AlphaFold3-predicted full-length models of the nAChR, rapsyn, and various rapsyn-nAChR complexes, identifying a consistent, asymmetric 3:1 binding architecture where each rapsyn is always sandwiched between the MX-MA loops from two subunits and where each phospho-tyrosine is lodged in a cationic pocket formed by conserved residues implicated in congenital myasthenic syndromes. The defined architecture fits published cryo-ET maps of Torpedo post-synaptic membranes and explains how both phosphorylated tyrosines and myasthenic syndrome-causing rapsyn mutations modulate receptor clustering.
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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) | 0.002 | 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".