Download MendeleyCryo-EM structures of the small-conductance Ca 2+ -activated K Ca 2.2 channel.
Nam, Y.W., Im, D., Garcia, A.S.C., Tringides, M.L., Nguyen, H.M., Liu, Y., Orfali, R., Ramanishka, A., Pintilie, G., Su, C.C., Cui, M., Logothetis, D.E., Yu, E.W., Wulff, H., Chandy, K.G., Zhang, M.(2025) Nat Commun 16: 3690-3690
- PubMed: 40246884
- DOI: https://doi.org/10.1038/s41467-025-59061-1
- Primary Citation of Related Structures:
8V2G, 8V2H, 8V3G, 9EIO - PubMed Abstract:
Small-conductance Ca 2+ -activated K + (K Ca 2.1-K Ca 2.3) channels modulate neuronal and cardiac excitability. We report cryo-electron microscopy structures of the K Ca 2.2 channel in complex with calmodulin and Ca 2+ , alone or bound to two small molecule inhibitors, at 3.18, 3.50, 2.99 and 2.97 angstrom resolution, respectively. Extracellular S3-S4 loops in β-hairpin configuration form an outer canopy over the pore with an aromatic box at the canopy's center. Each S3-S4 β-hairpin is tethered to the selectivity filter in the neighboring subunit by inter-subunit hydrogen bonds. This hydrogen bond network flips the aromatic residue (Tyr362) in the filter's GYG signature by 180°, causing the outer selectivity filter to widen and water to enter the filter. Disruption of the tether by a mutation narrows the outer selectivity filter, realigns Tyr362 to the position seen in other K + channels, and significantly increases unitary conductance. UCL1684, a mimetic of the bee venom peptide apamin, sits atop the canopy and occludes the opening in the aromatic box. AP14145, an analogue of a therapeutic for atrial fibrillation, binds in the central cavity below the selectivity filter and induces closure of the inner gate. These structures provide a basis for understanding the small unitary conductance and pharmacology of K Ca 2.x channels.
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA.
Organizational Affiliation:
