Human coronavirus HKU1 spike structures reveal the basis for sialoglycan specificity and carbohydrate-promoted conformational changes
Bibliographic record
Abstract
The human coronavirus HKU1 uses both sialoglycoconjugates and the protein transmembrane serine protease 2 (TMPRSS2) as receptors. Carbohydrate binding leads to the spike protein up conformation required for TMPRSS2 binding, an outcome suggesting a distinct mechanism for driving fusion of the viral and host cell membranes. Nevertheless, the conformational changes promoted by carbohydrate binding have not been fully elucidated and the basis for HKU1’s carbohydrate binding specificity remains unknown. Reported here are high resolution cryo-EM structures of the HKU1 spike protein trimer in its apo form and in complex with the carbohydrate moiety of a candidate carbohydrate receptor, the 9-O-acetylated GD3 ganglioside. The structures show that the spike monomer can exist in four discrete conformational states and that progression through them would promote the up conformation upon carbohydrate binding. We also show that a six-amino-acid insert is a determinant of HKU1’s specificity for gangliosides containing a 9-O-acetylated α2–8-linked disialic acid moiety and that HKU1 shows weak affinity for the 9-O-acetylated sialic acids found on decoy receptors such as mucins. Sialoglycan receptor binding promotes the D2 domain up conformation in the HKU1 coronavirus spike protein. Here the authors show that this conformational change is driven fundamentally by the full structuring of the canonical embecovirus binding site.
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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".