Download MendeleyStructural basis for the subtype-selective activation of K Ca 3.1 channels.
Ramanishka, A., Nasburg, J.A., Xu, Y., Ma, X., Mehvar, R., Cui, M., Nam, Y.W., Wulff, H., Zhang, M.(2026) Structure
- PubMed: 42140186 Search on PubMed
- DOI: https://doi.org/10.1016/j.str.2026.04.010
- Primary Citation Related Structures:
9ZPO, 9ZPT, 9ZRK, 9ZRL, 9ZRQ, 9ZRR - PubMed Abstract:
The intermediate-conductance (K Ca 3.1) and the small-conductance (K Ca 2.2) Ca 2+ -activated K + channels share a Ca 2+ -calmodulin dependent gating mechanism. We report cryo-electron microscopy structures of K Ca 3.1 and K Ca 2.2 in complex with two benzothiazole-type activators. While SKA-31 is only moderately selective (∼7.3-fold), its derivative SKA-111 exhibits ∼70-fold selectivity for K Ca 3.1 over K Ca 2.2. SKA-31 and SKA-111 both bind in a pocket at the interface between the S 45 A helix and calmodulin where they allosterically modulate the inner gate of the two channels. SKA-31 binds with comparable energies in the two channels, consistent with its moderate selectivity for K Ca 3.1 over K Ca 2.2. In the K Ca 3.1 structure, the calmodulin helix IV is positioned outward, forming a pocket that more readily accommodates the bulkier SKA-111 that sits deeper inside calmodulin's N-lobe in K Ca 3.1 than in K Ca 2.2. The resulting higher binding energy explains the improved selectivity of SKA-111 for K Ca 3.1 compared to the less selective SKA-31.
- Department of Basic Medical Sciences, University of Arizona College of Medicine, Phoenix, AZ 85004, USA; Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA 92618, USA.
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