Cryo-EM structures of the small-conductance Ca2+-activated KCa2.2 channel
Abstract Small-conductance Ca2+-activated K+ (KCa2.1-KCa2.3) channels modulate neuronal and cardiac excitability. We report cryo-electron microscopy structures of the KCa2.2 channel in complex with calmodulin and Ca2+, alone or bound to two small molecule inhibitors, at 3.18, 3.50, 2.99 and 2.97 ang...
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Nature Portfolio
2025-04-01
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| Series: | Nature Communications |
| Online Access: | https://doi.org/10.1038/s41467-025-59061-1 |
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| author | Young-Woo Nam Dohyun Im Ana Santa Cruz Garcia Marios L. Tringides Hai Minh Nguyen Yan Liu Razan Orfali Alena Ramanishka Grigore Pintilie Chih-Chia Su Meng Cui Diomedes E. Logothetis Edward W. Yu Heike Wulff K. George Chandy Miao Zhang |
| author_facet | Young-Woo Nam Dohyun Im Ana Santa Cruz Garcia Marios L. Tringides Hai Minh Nguyen Yan Liu Razan Orfali Alena Ramanishka Grigore Pintilie Chih-Chia Su Meng Cui Diomedes E. Logothetis Edward W. Yu Heike Wulff K. George Chandy Miao Zhang |
| author_sort | Young-Woo Nam |
| collection | DOAJ |
| description | Abstract Small-conductance Ca2+-activated K+ (KCa2.1-KCa2.3) channels modulate neuronal and cardiac excitability. We report cryo-electron microscopy structures of the KCa2.2 channel in complex with calmodulin and Ca2+, 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 KCa2.x channels. |
| format | Article |
| id | doaj-art-61a4bc0eef85447abdc8540066a7e2d5 |
| institution | DOAJ |
| issn | 2041-1723 |
| language | English |
| publishDate | 2025-04-01 |
| publisher | Nature Portfolio |
| record_format | Article |
| series | Nature Communications |
| spelling | doaj-art-61a4bc0eef85447abdc8540066a7e2d52025-08-20T03:18:53ZengNature PortfolioNature Communications2041-17232025-04-0116111310.1038/s41467-025-59061-1Cryo-EM structures of the small-conductance Ca2+-activated KCa2.2 channelYoung-Woo Nam0Dohyun Im1Ana Santa Cruz Garcia2Marios L. Tringides3Hai Minh Nguyen4Yan Liu5Razan Orfali6Alena Ramanishka7Grigore Pintilie8Chih-Chia Su9Meng Cui10Diomedes E. Logothetis11Edward W. Yu12Heike Wulff13K. George Chandy14Miao Zhang15Department of Biomedical and Pharmaceutical Sciences, Chapman University School of PharmacyDepartment of Cell Biology, Graduate School of Medicine, Kyoto UniversityDepartment of Pharmaceutical Sciences, Northeastern University School of Pharmacy and Pharmaceutical SciencesDepartment of Pharmacology, Case Western Reserve University School of MedicineDepartment of Pharmacology, School of Medicine, University of California DavisDivision of CryoEM and Bioimaging, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford UniversityDepartment of Biomedical and Pharmaceutical Sciences, Chapman University School of PharmacyDepartment of Biomedical and Pharmaceutical Sciences, Chapman University School of PharmacyDepartment of Bioengineering and Department of Microbiology and Immunology, Stanford UniversityDepartment of Pharmacology, Case Western Reserve University School of MedicineDepartment of Pharmaceutical Sciences, Northeastern University School of Pharmacy and Pharmaceutical SciencesDepartment of Pharmaceutical Sciences, Northeastern University School of Pharmacy and Pharmaceutical SciencesDepartment of Pharmacology, Case Western Reserve University School of MedicineDepartment of Pharmacology, School of Medicine, University of California DavisLKCMedicine-ICE Collaborative Platform, Lee Kong Chian School of Medicine, Nanyang Technological UniversityDepartment of Biomedical and Pharmaceutical Sciences, Chapman University School of PharmacyAbstract Small-conductance Ca2+-activated K+ (KCa2.1-KCa2.3) channels modulate neuronal and cardiac excitability. We report cryo-electron microscopy structures of the KCa2.2 channel in complex with calmodulin and Ca2+, 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 KCa2.x channels.https://doi.org/10.1038/s41467-025-59061-1 |
| spellingShingle | Young-Woo Nam Dohyun Im Ana Santa Cruz Garcia Marios L. Tringides Hai Minh Nguyen Yan Liu Razan Orfali Alena Ramanishka Grigore Pintilie Chih-Chia Su Meng Cui Diomedes E. Logothetis Edward W. Yu Heike Wulff K. George Chandy Miao Zhang Cryo-EM structures of the small-conductance Ca2+-activated KCa2.2 channel Nature Communications |
| title | Cryo-EM structures of the small-conductance Ca2+-activated KCa2.2 channel |
| title_full | Cryo-EM structures of the small-conductance Ca2+-activated KCa2.2 channel |
| title_fullStr | Cryo-EM structures of the small-conductance Ca2+-activated KCa2.2 channel |
| title_full_unstemmed | Cryo-EM structures of the small-conductance Ca2+-activated KCa2.2 channel |
| title_short | Cryo-EM structures of the small-conductance Ca2+-activated KCa2.2 channel |
| title_sort | cryo em structures of the small conductance ca2 activated kca2 2 channel |
| url | https://doi.org/10.1038/s41467-025-59061-1 |
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