9VU9: Channel D complex with 4

channel D complex with 4. Determined by electron microscopy at 3.34 Å resolution. Released 11 Mar 2026.

Method: Electron microscopy
Resolution: 3.34 Å
Organism: Homo sapiens
Chains: 7
Atoms: 11,823
Mol. weight: 306.48 kDa
Ligands: A1ETX
Released: 11 Mar 2026

Explore 9VU9 in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

9VU9 contains 76 α-helices and 8 β-strands across 7 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: 15 helices, 2 β-strands

Element	Residues	Length	Sheet
α-helix	119-155	37
α-helix	165-199	35
α-helix	205-207	3
α-helix	211-223	13
β-strand	234-240	7	1
β-strand	247-253	7	1
α-helix	255-259	5
α-helix	260-266	7
α-helix	267-275	9
α-helix	283-292	10
α-helix	298-308	11
α-helix	310-333	24
α-helix	345-356	12
α-helix	369-396	28
α-helix	401-434	34
α-helix	435-439	5
α-helix	445-472	28

Chain B: 16 helices, 2 β-strands

Element	Residues	Length	Sheet
α-helix	119-155	37
α-helix	165-199	35
α-helix	205-207	3
α-helix	211-223	13
β-strand	234-240	7	2
β-strand	247-253	7	2
α-helix	254-259	6
α-helix	260-266	7
α-helix	267-275	9
α-helix	283-291	9
α-helix	298-308	11
α-helix	310-333	24
α-helix	345-356	12
α-helix	369-396	28
α-helix	398-400	3
α-helix	401-434	34
α-helix	435-439	5
α-helix	445-472	28

Chain C: 16 helices, 2 β-strands

Element	Residues	Length	Sheet
α-helix	119-155	37
α-helix	165-199	35
α-helix	205-208	4
α-helix	211-223	13
β-strand	234-239	6	3
β-strand	248-253	6	3
α-helix	254-259	6
α-helix	260-266	7
α-helix	267-276	10
α-helix	283-292	10
α-helix	298-308	11
α-helix	310-333	24
α-helix	345-356	12
α-helix	369-396	28
α-helix	398-400	3
α-helix	401-434	34
α-helix	435-439	5
α-helix	445-472	28

Chain D: 14 helices, 2 β-strands

Element	Residues	Length	Sheet
α-helix	119-155	37
α-helix	165-199	35
α-helix	205-207	3
α-helix	211-223	13
β-strand	234-240	7	4
β-strand	247-253	7	4
α-helix	254-259	6
α-helix	260-266	7
α-helix	267-276	10
α-helix	278-281	4
α-helix	283-292	10
α-helix	298-308	11
α-helix	310-333	24
α-helix	334-336	3
α-helix	345-356	12
α-helix	369-396	28

Chain E: 5 helices, 0 β-strands

Element	Residues	Length
α-helix	83-90	8
α-helix	102-105	4
α-helix	106-111	6
α-helix	118-128	11
α-helix	138-145	8

Chain F: 5 helices, 0 β-strands

Element	Residues	Length
α-helix	83-90	8
α-helix	102-105	4
α-helix	106-112	7
α-helix	118-128	11
α-helix	138-145	8

Chain G: 5 helices, 0 β-strands

Element	Residues	Length
α-helix	83-90	8
α-helix	102-106	5
α-helix	107-112	6
α-helix	118-128	11
α-helix	138-144	7

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Calmodulin-1	E, F, G	protein	149	Homo sapiens	P0DP23 (AlphaFold model)
Small conductance calcium-activated potassium channel protein 2	A, B, C, D	protein	579	Homo sapiens	Q9H2S1 (AlphaFold model)

Sequence of entity 1 (E, F, G), FASTA

>9VU9_1 Calmodulin-1 (chains E, F, G)
MADQLTEEQIAEFKEAFSLFDKDGDGTITTKELGTVMRSLGQNPTEAELQDMINEVDADG
NGTIDFPEFLTMMARKMKDTDSEEEIREAFRVFDKDGNGYISAAELRHVMTNLGEKLTDE
EVDEMIREADIDGDGQVNYEEFVQMMTAK

Sequence of entity 2 (A, B, C, D), FASTA

>9VU9_2 Small conductance calcium-activated potassium channel protein 2 (chains A, B, C, D)
MSSCRYNGGVMRPLSNLSASRRNLHEMDSEAQPLQPPASVGGGGGASSPSAAAAAAAAVS
SSAPEIVVSKPEHNNSNNLALYGTGGGGSTGGGGGGGGSGHGSSSGTKSSKKKNQNIGYK
LGHRRALFEKRKRLSDYALIFGMFGIVVMVIETELSWGAYDKASLYSLALKCLISLSTII
LLGLIIVYHAREIQLFMVDNGADDWRIAMTYERIFFICLEILVCAIHPIPGNYTFTWTAR
LAFSYAPSTTTADVDIILSIPMFLRLYLIARVMLLHSKLFTDASSRSIGALNKINFNTRF
VMKTLMTICPGTVLLVFSISLWIIAAWTVRACERYHDQQDVTSNFLGAMWLISITFLSIG
YGDMVPNTYCGKGVCLLTGIMGAGCTALVVAVVARKLELTKAEKHVHNFMMDTQLTKRVK
NAAANVLRETWLIYKNTKLVKKIDHAKVRKHQRKFLQAIHQLRSVKMEQRKLNDQANTLV
DLAKTQNIMYDMISDLNERSEDFEKRIVTLETKLETLIGSIHALPGLISQTIRQQQRDFI
EAQMESYDKHVTYNAERSRSSSRRRRSSSTAPPTSSESS

Ligands and cofactors

ID	Name	Formula	Copies
A1ETX	(3~{S})-3-(1~{H}-benzimidazol-2-ylamino)-~{N}-(cyanomethyl)-~{N}-methyl-3-[3-(t…	C20 H18 F3 N5 O	1

Water and common crystallization additives (K) are not listed.

Primary citation

Structural mechanisms for inhibition and activation of human small-conductance Ca 2+ -activated potassium channel SK2. Ma, B., Wu, D., Cao, E. et al. Nat Commun (2026) 17:1770-1770. DOI 10.1038/s41467-026-68475-4 · PubMed

Other PDB entries of the same protein (UniProt P0DP23 (AlphaFold model), which also has an AlphaFold model), best resolution first:

9MXD 1.17 Å, Human E104A calmodulin:MLCK RM20 complex
7BF1 1.24 Å, Ca2+-Calmodulin in complex with peptide from brain-type creatine kinase in extended 1:2…
6XXX 1.25 Å, 1.25 Angstrom crystal structure of Ca/CaM A102V:RyR2 peptide complex
4DJC 1.35 Å, 1.35 A crystal structure of the NaV1.5 DIII-IV-Ca/CaM complex
7BF2 1.43 Å, Ca2+-Calmodulin in complex with human muscle form creatine kinase peptide in extended…
2F3Y 1.45 Å, Calmodulin/IQ domain complex
2W73 1.45 Å, High-resolution structure of the complex between calmodulin and a peptide from…
4LZX 1.5 Å, Complex of IQCG and Ca2+-free CaM
5V03 1.58 Å, A positive allosteric modulator binding pocket in SK2 ion channels is shared by Riluzole…
9MVW 1.58 Å, Crystal structure of S101F calmodulin - CaM:RM20 analog complex
2F3Z 1.6 Å, Calmodulin/IQ-AA domain complex
6M7H 1.6 Å, Structure of calmodulin with KN93

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