Cryo-EM structure of the human SK2-4 chimera/calmodulin channel complex bound to a small molecule activator. Determined by electron microscopy at 3.1 Å resolution. Released 9 Jul 2025.
Explore 9O5O in 3D Show helices and sheets RCSB PDB PDBe
9O5O contains 92 α-helices and 24 β-strands across 8 chains. Residue ranges use author residue numbering, as in the PDB file, from PDBe. To see them in 3D, choose the Cartoon representation with Secondary structure coloring: helices, sheets and coils get different colors.
| Element | Residues | Length | Sheet |
|---|---|---|---|
| α-helix | 119-158 | 40 | |
| α-helix | 165-199 | 35 | |
| α-helix | 205-208 | 4 | |
| α-helix | 211-224 | 14 | |
| β-strand | 234-240 | 7 | 1 |
| β-strand | 247-253 | 7 | 1 |
| α-helix | 255-259 | 5 | |
| α-helix | 260-266 | 7 | |
| α-helix | 267-276 | 10 | |
| α-helix | 278-281 | 4 | |
| α-helix | 283-291 | 9 | |
| α-helix | 298-308 | 11 | |
| α-helix | 310-332 | 23 | |
| α-helix | 345-356 | 12 | |
| α-helix | 369-392 | 24 | |
| α-helix | 401-438 | 38 | |
| α-helix | 443-475 | 33 |
| Element | Residues | Length | Sheet |
|---|---|---|---|
| α-helix | 6-19 | 14 | |
| β-strand | 27 | 1 | 2 |
| α-helix | 29-38 | 10 | |
| α-helix | 45-52 | 8 | |
| β-strand | 63 | 1 | 2 |
| α-helix | 65-75 | 11 | |
| α-helix | 81-92 | 12 | |
| β-strand | 100 | 1 | 3 |
| α-helix | 102-108 | 7 | |
| α-helix | 119-128 | 10 | |
| β-strand | 136 | 1 | 3 |
| α-helix | 138-145 | 8 |
| Molecule | Chains | Type | Length | Organism | UniProt |
|---|---|---|---|---|---|
| Intermediate conductance calcium-activated potassium channel protein 4,Small conductance… | A, B, C, D | protein | 435 | Homo sapiens | O15554 (AlphaFold model), Q9H2S1 (AlphaFold model) |
| Calmodulin-1 | E, F, G, H | protein | 149 | Homo sapiens | P0DP23 (AlphaFold model) |
>9O5O_1 Intermediate conductance calcium-activated potassium channel protein 4,Small conductance calcium-activated potassium channel protein 2 chimera (chains A, B, C, D) MGGDLVLGLGALRRRRALFEKRKRLSDYALIFGMFGIVVMVIETELSWGAYDKASLYSLA LKCLISLSTIILLGLIIVYHAREIQLFMVDNGADDWRIAMTYERIFFICLEILVCAIHPI PGNYTFTWTARLAFSYAPSTTTADVDIILSIPMFLRLYLIARVMLLHSKLFTDASSRSIG ALNKINFNTRFVMKTLMTICPGTVLLVFSISLWIIAAWTVRACERYHDQQDVTSNFLGAM WLISITFLSIGYGDMVPNTYCGKGVCLLTGIMGAGCTALVVAVVARKLELTKAEKHVHNF MMDIQYTKEMKESAARVLQEAWMFYKHTRRKESHAARRHQRKLLAAINAFRQVRLKHRKL REQVNSMVDISKMHMILYDLQQNLSSSHRALEKQIDTLAGKLDALTELLSTALGPRQLPE PSQQSKSSSLEVLFQ
>9O5O_2 Calmodulin-1 (chains E, F, G, H) MADQLTEEQIAEFKEAFSLFDKDGDGTITTKELGTVMRSLGQNPTEAELQDMINEVDADG NGTIDFPEFLTMMARKMKDTDSEEEIREAFRVFDKDGNGYISAAELRHVMTNLGEKLTDE EVDEMIREADIDGDGQVNYEEFVQMMTAK
| ID | Name | Formula | Copies |
|---|---|---|---|
| A1B8G | N-(2,1,3-benzoxadiazol-4-yl)-4-(trifluoromethyl)benzamide | C14 H8 F3 N3 O2 | 4 |
| CA | Calcium ion | Ca | 16 |
Water and common crystallization additives (K) are not listed.
Mechanism of SK2 channel gating and its modulation by the bee toxin apamin and small molecules. Cassell, S.J., Li, W., Krautwald, S. et al. Elife (2025) 14. DOI 10.7554/eLife.107733 · PubMed
Other PDB entries of the same protein (UniProt O15554 (AlphaFold model), which also has an AlphaFold model), best resolution first:
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