9ZRL: KCa3.1_II/calmodulin channel
Cryo-EM structure of KCa3.1_II/calmodulin channel in complex with SKA111. Determined by electron microscopy at 3.38 Å resolution. Released 14 Jan 2026.
- Method
- Electron microscopy
- Resolution
- 3.38 Å
- Organism
- Homo sapiens
- Chains
- 8
- Atoms
- 11,999
- Mol. weight
- 185.82 kDa
- Released
- 14 Jan 2026
Explore 9ZRL in 3D
Show helices and sheets
RCSB PDB
PDBe
Secondary structure: helices and β-sheets
9ZRL contains 82 α-helices and 8 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: 16 helices, 0 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 13-23 | 11 | |
| α-helix | 29-49 | 21 | |
| α-helix | 55-91 | 37 | |
| α-helix | 102-114 | 13 | |
| α-helix | 143-146 | 4 | |
| α-helix | 149-154 | 6 | |
| α-helix | 155-161 | 7 | |
| α-helix | 163-171 | 9 | |
| α-helix | 177-185 | 9 | |
| α-helix | 192-202 | 11 | |
| α-helix | 204-213 | 10 | |
| α-helix | 219-226 | 8 | |
| α-helix | 237-248 | 12 | |
| α-helix | 263-287 | 25 | |
| α-helix | 293-326 | 34 | |
| α-helix | 334-368 | 35 | |
Chain B: 16 helices, 0 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 13-25 | 13 | |
| α-helix | 28-49 | 22 | |
| α-helix | 57-87 | 31 | |
| α-helix | 103-115 | 13 | |
| α-helix | 147-154 | 8 | |
| α-helix | 155-161 | 7 | |
| α-helix | 162-170 | 9 | |
| α-helix | 172-175 | 4 | |
| α-helix | 177-186 | 10 | |
| α-helix | 194-202 | 9 | |
| α-helix | 204-207 | 4 | |
| α-helix | 209-226 | 18 | |
| α-helix | 237-248 | 12 | |
| α-helix | 263-287 | 25 | |
| α-helix | 293-330 | 38 | |
| α-helix | 335-368 | 34 | |
Chain C: 16 helices, 0 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 10-14 | 5 | |
| α-helix | 15-50 | 36 | |
| α-helix | 60-87 | 28 | |
| α-helix | 102-114 | 13 | |
| α-helix | 147-153 | 7 | |
| α-helix | 154-162 | 9 | |
| α-helix | 163-170 | 8 | |
| α-helix | 177-184 | 8 | |
| α-helix | 185-187 | 3 | |
| α-helix | 192-202 | 11 | |
| α-helix | 204-207 | 4 | |
| α-helix | 209-226 | 18 | |
| α-helix | 237-248 | 12 | |
| α-helix | 263-287 | 25 | |
| α-helix | 293-326 | 34 | |
| α-helix | 336-368 | 33 | |
Chain D: 18 helices, 0 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 13-24 | 12 | |
| α-helix | 28-49 | 22 | |
| α-helix | 55-87 | 33 | |
| α-helix | 88-92 | 5 | |
| α-helix | 96-98 | 3 | |
| α-helix | 102-115 | 14 | |
| α-helix | 144-146 | 3 | |
| α-helix | 149-154 | 6 | |
| α-helix | 155-161 | 7 | |
| α-helix | 162-170 | 9 | |
| α-helix | 177-186 | 10 | |
| α-helix | 192-202 | 11 | |
| α-helix | 204-207 | 4 | |
| α-helix | 209-226 | 18 | |
| α-helix | 237-248 | 12 | |
| α-helix | 263-287 | 25 | |
| α-helix | 293-330 | 38 | |
| α-helix | 334-368 | 35 | |
Chain E: 4 helices, 2 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 88-91 | 4 | |
| β-strand | 100 | 1 | 1 |
| α-helix | 102-109 | 8 | |
| α-helix | 121-127 | 7 | |
| β-strand | 136 | 1 | 1 |
| α-helix | 139-143 | 5 | |
Chain F: 4 helices, 2 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 88-91 | 4 | |
| β-strand | 100 | 1 | 2 |
| α-helix | 102-110 | 9 | |
| α-helix | 118-127 | 10 | |
| β-strand | 136 | 1 | 2 |
| α-helix | 139-146 | 8 | |
Chain G: 4 helices, 2 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 88-91 | 4 | |
| β-strand | 100-101 | 2 | 3 |
| α-helix | 102-110 | 9 | |
| α-helix | 118-126 | 9 | |
| β-strand | 135-136 | 2 | 3 |
| α-helix | 139-146 | 8 | |
Chain H: 4 helices, 2 β-strands
| Element | Residues | Length | Sheet |
|---|
| α-helix | 88-91 | 4 | |
| β-strand | 100 | 1 | 4 |
| α-helix | 102-110 | 9 | |
| α-helix | 118-128 | 11 | |
| β-strand | 136 | 1 | 4 |
| α-helix | 139-146 | 8 | |
Molecules and chains
| Molecule | Chains | Type | Length | Organism | UniProt |
|---|
| Intermediate conductance calcium-activated potassium channel protein 4 | A, B, C, D | protein | 343 | Homo sapiens | O15554 (AlphaFold model) |
| Calmodulin-1 | E, F, G, H | protein | 67 | Homo sapiens | P0DP23 (AlphaFold model) |
Sequence of entity 1 (A, B, C, D), FASTA
>9ZRL_1 Intermediate conductance calcium-activated potassium channel protein 4 (chains A, B, C, D)
LGALRRRKRLLEQEKSLAGWALVLAGTGIGLMVLHAEMLWFGGCSWALYLFLVKCTISIS
TFLLLCLIVAFHAKEVQLFMTDNGLRDWRVALTGRQAAQIVLELVVCGLHPAPVRPGFLG
QGEALLSLAMLLRLYLVPRAVLLRSGVLLNASYRSIGALNQVRFRHWFVAKLYMNTHPGR
LLLGLTLGLWLTTAWVLSVAERQAVNATGHLSDTLWLIPITFLTIGYGDVVPGTMWGKIV
CLCTGVMGVCCTALLVAVVARKLEFNKAEKHVHNFMMDIQYTKEMKESAARVLQEAWMFY
KHTRRKESHAARRHQRKLLAAINAFRQVRLKHRKLREQVNSMV
Sequence of entity 2 (E, F, G, H), FASTA
>9ZRL_2 Calmodulin-1 (chains E, F, G, H)
SEEEIREAFRVFDKDGNGYISAAELRHVMTNLGEKLTDEEVDEMIREADIDGDGQVNYEE
FVQMMTA
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 O15554 (AlphaFold model), which also has an AlphaFold model), best resolution first:
- 6D42 1.75 Å, Crystal structure of the KCa3.1 C-terminal four-helix bundle (with copper)
- 9ZRK 2.99 Å, Cryo-EM structure of KCa3.1_I/calmodulin channel in complex with SKA111.
- 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…
- 9O53 3.3 Å, Cryo-EM structure of the human SK2-4 chimera/calmodulin channel complex bound to a small…
- 9ZPT 3.39 Å, Cryo-EM structure of KCa3.1_II/calmodulin channel in complex with SKA31.
- 6CNM 3.4 Å, Cryo-EM structure of the human SK4/calmodulin channel complex
- 9O51 3.4 Å, Cryo-EM structure of the human SK2-4 chimera/calmodulin channel complex in the Ca2+ free…
- 9YDZ 3.4 Å, Cryo EM structure of KCa3.1_R355K_II/calmodulin channel in complex with rimtuzalcap
- 6CNN 3.5 Å, Cryo-EM structure of the human SK4/calmodulin channel complex in the Ca2+ bound state I
- 9ED1 3.5 Å, Cryo-EM structure of the human KCa3.1/calmodulin channel in complex with Ca2+ and…
Browse structure collections
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