9ZRR: KCa2.2/calmodulin channel
Cryo-EM structure of KCa2.2/calmodulin channel in complex with SKA111. Determined by electron microscopy at 3.31 Å resolution. Released 27 May 2026.
- Method
- Electron microscopy
- Resolution
- 3.31 Å
- Organism
- Homo sapiens
- Chains
- 8
- Atoms
- 16,173
- Mol. weight
- 231.27 kDa
- Ligands
- A1C3U, CA
- Released
- 27 May 2026
Explore 9ZRR in 3D
Show helices and sheets
RCSB PDB
PDBe
Secondary structure: helices and β-sheets
9ZRR contains 99 α-helices and 20 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.
Chain A: 17 helices, 2 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 119-129 | 11 | |
| α-helix | 133-156 | 24 | |
| α-helix | 172-177 | 6 | |
| α-helix | 181-200 | 20 | |
| α-helix | 207-209 | 3 | |
| α-helix | 212-225 | 14 | |
| β-strand | 235-241 | 7 | 1 |
| β-strand | 248-254 | 7 | 1 |
| α-helix | 261-268 | 8 | |
| α-helix | 269-276 | 8 | |
| α-helix | 284-292 | 9 | |
| α-helix | 299-309 | 11 | |
| α-helix | 311-334 | 24 | |
| α-helix | 346-357 | 12 | |
| α-helix | 370-397 | 28 | |
| α-helix | 402-409 | 8 | |
| α-helix | 413-421 | 9 | |
| α-helix | 425-433 | 9 | |
| α-helix | 446-476 | 31 | |
Chain B: 17 helices, 2 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 121-125 | 5 | |
| α-helix | 133-156 | 24 | |
| α-helix | 166-200 | 35 | |
| α-helix | 207-209 | 3 | |
| α-helix | 217-225 | 9 | |
| β-strand | 235-241 | 7 | 2 |
| β-strand | 248-254 | 7 | 2 |
| α-helix | 261-267 | 7 | |
| α-helix | 268-276 | 9 | |
| α-helix | 279-282 | 4 | |
| α-helix | 284-291 | 8 | |
| α-helix | 302-309 | 8 | |
| α-helix | 311-334 | 24 | |
| α-helix | 346-357 | 12 | |
| α-helix | 370-397 | 28 | |
| α-helix | 402-409 | 8 | |
| α-helix | 413-438 | 26 | |
| α-helix | 446-449 | 4 | |
| α-helix | 453-477 | 25 | |
Chain C: 15 helices, 2 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 133-156 | 24 | |
| α-helix | 166-201 | 36 | |
| α-helix | 207-209 | 3 | |
| α-helix | 212-225 | 14 | |
| β-strand | 235-241 | 7 | 3 |
| α-helix | 242 | 1 | |
| β-strand | 248-254 | 7 | 3 |
| α-helix | 261-268 | 8 | |
| α-helix | 269-276 | 8 | |
| α-helix | 284-290 | 7 | |
| α-helix | 299-309 | 11 | |
| α-helix | 311-334 | 24 | |
| α-helix | 346-357 | 12 | |
| α-helix | 370-397 | 28 | |
| α-helix | 402-409 | 8 | |
| α-helix | 413-439 | 27 | |
| α-helix | 446-477 | 32 | |
Chain D: 18 helices, 2 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 121-125 | 5 | |
| α-helix | 133-156 | 24 | |
| α-helix | 173-197 | 25 | |
| α-helix | 198-202 | 5 | |
| α-helix | 207-209 | 3 | |
| α-helix | 212-225 | 14 | |
| β-strand | 235-241 | 7 | 4 |
| β-strand | 248-254 | 7 | 4 |
| α-helix | 261-267 | 7 | |
| α-helix | 268-276 | 9 | |
| α-helix | 279-282 | 4 | |
| α-helix | 284-292 | 9 | |
| α-helix | 299-309 | 11 | |
| α-helix | 311-328 | 18 | |
| α-helix | 331-334 | 4 | |
| α-helix | 346-357 | 12 | |
| α-helix | 370-397 | 28 | |
| α-helix | 402-416 | 15 | |
| α-helix | 419-437 | 19 | |
| α-helix | 446-477 | 32 | |
Chain E: 8 helices, 2 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 6-17 | 12 | |
| β-strand | 27 | 1 | 5 |
| α-helix | 29-39 | 11 | |
| α-helix | 45-50 | 6 | |
| β-strand | 63 | 1 | 5 |
| α-helix | 65-76 | 12 | |
| α-helix | 81-85 | 5 | |
| α-helix | 103-111 | 9 | |
| α-helix | 118-128 | 11 | |
| α-helix | 139-144 | 6 | |
Chain F: 8 helices, 2 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 6-17 | 12 | |
| β-strand | 27 | 1 | 6 |
| α-helix | 29-39 | 11 | |
| α-helix | 45-55 | 11 | |
| β-strand | 63 | 1 | 6 |
| α-helix | 65-75 | 11 | |
| α-helix | 81-90 | 10 | |
| α-helix | 102-111 | 10 | |
| α-helix | 118-125 | 8 | |
| α-helix | 140-143 | 4 | |
Chain G: 8 helices, 4 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 6-17 | 12 | |
| β-strand | 27 | 1 | 7 |
| α-helix | 29-39 | 11 | |
| α-helix | 45-54 | 10 | |
| β-strand | 63 | 1 | 7 |
| α-helix | 65-76 | 12 | |
| α-helix | 81-90 | 10 | |
| β-strand | 100 | 1 | 8 |
| α-helix | 102-111 | 10 | |
| α-helix | 118-125 | 8 | |
| β-strand | 136 | 1 | 8 |
| α-helix | 140-143 | 4 | |
Chain H: 8 helices, 4 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 6-17 | 12 | |
| β-strand | 27 | 1 | 9 |
| α-helix | 29-39 | 11 | |
| α-helix | 45-52 | 8 | |
| β-strand | 63 | 1 | 9 |
| α-helix | 65-75 | 11 | |
| α-helix | 81-90 | 10 | |
| β-strand | 100 | 1 | 10 |
| α-helix | 102-111 | 10 | |
| α-helix | 118-128 | 11 | |
| β-strand | 136 | 1 | 10 |
| α-helix | 140-143 | 4 | |
Molecules and chains
| Molecule | Chains | Type | Length | Organism | UniProt |
|---|
| Small conductance calcium-activated potassium channel protein 2 | A, B, C, D | protein | 361 | Homo sapiens | Q9H2S1 (AlphaFold model) |
| Calmodulin-1 | E, F, G, H | protein | 144 | Homo sapiens | P0DP23 (AlphaFold model) |
Sequence of entity 1 (A, B, C, D), FASTA
>9ZRR_1 Small conductance calcium-activated potassium channel protein 2 (chains A, B, C, D)
IGYKLGHRRALFEKRKRLSDYALIFGMFGIVVMVIETELSWGAYDKASLYSLALKCLISL
STIILLGLIIVYHAREIQLFMVDNGADDWRIAMTYERIFFICLEILVCAIHPIPGNYTFT
WTARLAFSYAPSTTTADVDIILSIPMFLRLYLIARVMLLHSKLFTDASSRSIGALNKINF
NTRFVMKTLMTICPGTVLLVFSISLWIIAAWTVRACERYHDQQDVTSNFLGAMWLISITF
LSIGYGDMVPNTYCGKGVCLLTGIMGAGCTALVVAVVARKLELTKAEKHVHNFMMDTQLT
KRVKNAAANVLRETWLIYKNTKLVKKIDHAKVRKHQRKFLQAIHQLRSVKMEQRKLNDQA
N
Sequence of entity 2 (E, F, G, H), FASTA
>9ZRR_2 Calmodulin-1 (chains E, F, G, H)
DQLTEEQIAEFKEAFSLFDKDGDGTITTKELGTVMRSLGQNPTEAELQDMINEVDADGNG
TIDFPEFLTMMARKMKDTDSEEEIREAFRVFDKDGNGYISAAELRHVMTNLGEKLTDEEV
DEMIREADIDGDGQVNYEEFVQMM
Ligands and cofactors
| ID | Name | Formula | Copies |
|---|
| A1C3U | 5-methylnaphtho[1,2-d][1,3]thiazol-2-amine | C12 H10 N2 S | 4 |
| CA | Calcium ion | Ca | 12 |
Water and common crystallization additives (K) are not listed.
Primary citation
Structural basis for the subtype-selective activation of K Ca 3.1 channels. Ramanishka, A., Nasburg, J.A., Xu, Y. et al. Structure (2026) 34:1040-1049.e3. DOI 10.1016/j.str.2026.04.010 · PubMed
Other PDB entries of the same protein (UniProt Q9H2S1 (AlphaFold model), which also has an AlphaFold model), best resolution first:
- 5V03 1.58 Å, A positive allosteric modulator binding pocket in SK2 ion channels is shared by Riluzole…
- 5V02 1.78 Å, A positive allosteric modulator binding pocket in SK2 ion channels is shared by Riluzole…
- 5WBX 1.9 Å, Structural insights into the potency of SK/IK channel positive modulators
- 5WC5 2.3 Å, Structural insights into the potency of SK/IK channel positive modulators
- 6ALE 2.5 Å, A V-to-F substitution in SK2 channels causes Ca2+ hypersensitivity and improves…
- 9ZRQ 2.77 Å, Cryo-EM structure of KCa2.2/calmodulin channel in complex with SKA31.
- 9VUC 2.96 Å, channel B complex with 2
- 9O48 3.1 Å, Cryo-EM structure of the human SK2-4 chimera/calmodulin channel complex in the Ca2+…
- 9O5O 3.1 Å, Cryo-EM structure of the human SK2-4 chimera/calmodulin channel complex bound to a small…
- 9O52 3.18 Å, Cryo-EM structure of the human SK2-4 chimera/calmodulin channel complex bound to the bee…
- 9VUA 3.23 Å, channel A complex with 1
- 9O53 3.3 Å, Cryo-EM structure of the human SK2-4 chimera/calmodulin channel complex bound to a small…
Browse structure collections
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