9O85: KCa2.2_I/calmodulin channel
Cryo-EM structure of KCa2.2_I/calmodulin channel in complex with rimtuzalcap. Determined by electron microscopy at 3.13 Å resolution. Released 18 Jun 2025.
- Method
- Electron microscopy
- Resolution
- 3.13 Å
- Organism
- Rattus norvegicus
- Chains
- 8
- Atoms
- 16,419
- Mol. weight
- 240.46 kDa
- Ligands
- CA, A1B92
- Released
- 18 Jun 2025
Explore 9O85 in 3D
Show helices and sheets
RCSB PDB
PDBe
Secondary structure: helices and β-sheets
9O85 contains 102 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.
Chain A: 17 helices, 2 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 126-156 | 31 | |
| α-helix | 166-200 | 35 | |
| α-helix | 206-209 | 4 | |
| α-helix | 212-225 | 14 | |
| β-strand | 235-241 | 7 | 1 |
| β-strand | 248-254 | 7 | 1 |
| α-helix | 256-260 | 5 | |
| α-helix | 261-267 | 7 | |
| α-helix | 268-276 | 9 | |
| α-helix | 284-292 | 9 | |
| α-helix | 299-309 | 11 | |
| α-helix | 311-334 | 24 | |
| α-helix | 346-357 | 12 | |
| α-helix | 370-396 | 27 | |
| α-helix | 402-423 | 22 | |
| α-helix | 426-438 | 13 | |
| α-helix | 448-477 | 30 | |
| α-helix | 478-480 | 3 | |
| α-helix | 485-498 | 14 | |
Chain B: 16 helices, 2 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 124-156 | 33 | |
| α-helix | 166-200 | 35 | |
| α-helix | 206-209 | 4 | |
| α-helix | 212-225 | 14 | |
| β-strand | 235-241 | 7 | 2 |
| β-strand | 248-254 | 7 | 2 |
| α-helix | 256-260 | 5 | |
| α-helix | 261-267 | 7 | |
| α-helix | 268-276 | 9 | |
| α-helix | 284-292 | 9 | |
| α-helix | 299-309 | 11 | |
| α-helix | 311-333 | 23 | |
| α-helix | 346-357 | 12 | |
| α-helix | 370-396 | 27 | |
| α-helix | 402-414 | 13 | |
| α-helix | 418-439 | 22 | |
| α-helix | 446-477 | 32 | |
| α-helix | 485-497 | 13 | |
Chain C: 16 helices, 2 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 129-156 | 28 | |
| α-helix | 166-200 | 35 | |
| α-helix | 206-209 | 4 | |
| α-helix | 212-225 | 14 | |
| β-strand | 235-241 | 7 | 3 |
| β-strand | 248-254 | 7 | 3 |
| α-helix | 256-260 | 5 | |
| α-helix | 261-267 | 7 | |
| α-helix | 268-276 | 9 | |
| α-helix | 284-292 | 9 | |
| α-helix | 299-309 | 11 | |
| α-helix | 311-333 | 23 | |
| α-helix | 346-357 | 12 | |
| α-helix | 370-396 | 27 | |
| α-helix | 402-439 | 38 | |
| α-helix | 446-465 | 20 | |
| α-helix | 469-477 | 9 | |
| α-helix | 485-497 | 13 | |
Chain D: 17 helices, 2 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 129-156 | 28 | |
| α-helix | 166-200 | 35 | |
| α-helix | 206-208 | 3 | |
| α-helix | 212-225 | 14 | |
| β-strand | 235-241 | 7 | 4 |
| β-strand | 248-254 | 7 | 4 |
| α-helix | 256-260 | 5 | |
| α-helix | 261-267 | 7 | |
| α-helix | 268-276 | 9 | |
| α-helix | 284-292 | 9 | |
| α-helix | 299-309 | 11 | |
| α-helix | 311-333 | 23 | |
| α-helix | 346-357 | 12 | |
| α-helix | 370-396 | 27 | |
| α-helix | 402-439 | 38 | |
| α-helix | 446-465 | 20 | |
| α-helix | 469-477 | 9 | |
| α-helix | 478-480 | 3 | |
| α-helix | 485-498 | 14 | |
Chain E: 10 helices, 4 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 6-10 | 5 | |
| α-helix | 13-19 | 7 | |
| β-strand | 27 | 1 | 5 |
| α-helix | 29-37 | 9 | |
| α-helix | 45-53 | 9 | |
| β-strand | 63 | 1 | 5 |
| α-helix | 65-72 | 8 | |
| α-helix | 82-91 | 10 | |
| β-strand | 100-101 | 2 | 6 |
| α-helix | 102-111 | 10 | |
| α-helix | 115-117 | 3 | |
| α-helix | 118-126 | 9 | |
| β-strand | 135-136 | 2 | 6 |
| α-helix | 140-146 | 7 | |
Chain F: 8 helices, 4 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 6-19 | 14 | |
| β-strand | 27 | 1 | 7 |
| α-helix | 29-37 | 9 | |
| α-helix | 45-53 | 9 | |
| β-strand | 63 | 1 | 7 |
| α-helix | 65-69 | 5 | |
| α-helix | 81-91 | 11 | |
| β-strand | 99-101 | 3 | 8 |
| α-helix | 102-111 | 10 | |
| α-helix | 115-117 | 3 | |
| α-helix | 118-128 | 11 | |
| β-strand | 135-137 | 3 | 8 |
Chain G: 9 helices, 4 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 6-10 | 5 | |
| α-helix | 16-19 | 4 | |
| β-strand | 27 | 1 | 9 |
| α-helix | 29-38 | 10 | |
| α-helix | 45-55 | 11 | |
| β-strand | 63 | 1 | 9 |
| α-helix | 65-74 | 10 | |
| α-helix | 81-91 | 11 | |
| β-strand | 99 | 1 | 10 |
| α-helix | 102-111 | 10 | |
| α-helix | 118-128 | 11 | |
| β-strand | 137 | 1 | 10 |
| α-helix | 139-145 | 7 | |
Chain H: 9 helices, 4 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 6-19 | 14 | |
| β-strand | 27 | 1 | 11 |
| α-helix | 31-38 | 8 | |
| α-helix | 45-53 | 9 | |
| β-strand | 63 | 1 | 11 |
| α-helix | 64 | 1 | |
| α-helix | 65-72 | 8 | |
| α-helix | 81-91 | 11 | |
| β-strand | 99 | 1 | 12 |
| α-helix | 102-111 | 10 | |
| α-helix | 118-126 | 9 | |
| β-strand | 137 | 1 | 12 |
| 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 | 380 | Rattus norvegicus | P70604 (AlphaFold model) |
| Calmodulin-1 | E, F, G, H | protein | 144 | Rattus norvegicus | P0DP29 (AlphaFold model) |
Sequence of entity 1 (A, B, C, D), FASTA
>9O85_1 Small conductance calcium-activated potassium channel protein 2 (chains A, B, C, D)
KLGHRRALFEKRKRLSDYALIFGMFGIVVMVIETELSWGAYDKASLYSLALKCLISLSTI
ILLGLIIVYHAREIQLFMVDNGADDWRIAMTYERIFFICLEILVCAIHPIPGNYTFTWTA
RLAFSYAPSTTTADVDIILSIPMFLRLYLIARVMLLHSKLFTDASSRSIGALNKINFNTR
FVMKTLMTICPGTVLLVFSISLWIIAAWTVRACERYHDQQDVTSNFLGAMWLISITFLSI
GYGDMVPNTYCGKGVCLLTGIMGAGCTALVVAVVARKLELTKAEKHVHNFMMDTQLTKRV
KNAAANVLRETWLIYKNTKLVKKIDHAKVRKHQRKFLQAIHQLRSVKMEQRKLNDQANTL
VDLAKTQNIMYDMISDLNER
Sequence of entity 2 (E, F, G, H), FASTA
>9O85_2 Calmodulin-1 (chains E, F, G, H)
LTEEQIAEFKEAFSLFDKDGDGTITTKELGTVMRSLGQNPTEAELQDMINEVDADGNGTI
DFPEFLTMMARKMKDTDSEEEIREAFRVFDKDGNGYISAAELRHVMTNLGEKLTDEEVDE
MIREADIDGDGQVNYEEFVQMMTA
Ligands and cofactors
| ID | Name | Formula | Copies |
|---|
| CA | Calcium ion | Ca | 8 |
| A1B92 | Rimtuzalcap | C18 H24 F2 N6 O | 4 |
Water and common crystallization additives (K) are not listed.
Primary citation
Structural basis for the subtype-selectivity of K Ca 2.2 channel activators. Nam, Y.W., Ramanishka, A., Xu, Y. et al. Nat Commun (2026) 17:531-531. DOI 10.1038/s41467-025-67232-3 · PubMed
Other PDB entries of the same protein (UniProt P70604 (AlphaFold model), which also has an AlphaFold model), best resolution first:
- 4J9Y 1.51 Å, Calcium-calmodulin complexed with the calmodulin binding domain from a small conductance…
- 1G4Y 1.6 Å, 1.60 a crystal structure of the gating domain from small conductance potassium channel…
- 4G28 1.63 Å, Calcium-calmodulin complexed with the calmodulin binding domain from a small conductance…
- 4G27 1.65 Å, Calcium-calmodulin complexed with the calmodulin binding domain from a small conductance…
- 4J9Z 1.66 Å, Calcium-calmodulin complexed with the calmodulin binding domain from a small conductance…
- 3SJQ 1.9 Å, Crystal structure of a small conductance potassium channel splice variant complexed with…
- 4QNH 2.02 Å, Calcium-calmodulin (T79D) complexed with the calmodulin binding domain from a small…
- 2PNV 2.1 Å, Crystal Structure of the leucine zipper domain of small-conductance Ca2+-activated K+…
- 6CZQ 2.2 Å, A V-to-F substitution in SK2 channels causes Ca2+ hypersensitivity and improves…
- 9O7S 2.71 Å, Cryo-EM structure of KCa2.2/calmodulin channel in complex with NS309
- 9O93 2.96 Å, Cryo-EM structure of KCa2.2_II/calmodulin channel in complex with rimtuzalcap
- 1QX7 3.09 Å, Crystal structure of apoCaM bound to the gating domain of small conductance…
Browse structure collections
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