12DK: Human KCNQ1-CaM-PIP2 intermediate state

structure of human KCNQ1-CaM-PIP2 intermediate state. Determined by electron microscopy at 3.47 Å resolution. Released 6 May 2026.

Method: Electron microscopy
Resolution: 3.47 Å
Organism: Homo sapiens
Chains: 8
Atoms: 15,464
Mol. weight: 319.7 kDa
Ligands: PT5, CA
Released: 6 May 2026

Explore 12DK in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

12DK contains 112 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.

Chains A, C, E and G: 20 helices, 2 β-strands

Element	Residues	Length	Sheet
α-helix	105-115	11
α-helix	121-144	24
α-helix	154-177	24
α-helix	178-180	3
α-helix	182-184	3
α-helix	186-194	9
α-helix	197-215	19
α-helix	230-239	10
α-helix	246-257	12
α-helix	259-283	25
β-strand	288	1	1
β-strand	294	1	1
α-helix	299-310	12
α-helix	323-336	14
α-helix	338-359	22
α-helix	361-363	3
α-helix	364-367	4
α-helix	368-383	16
α-helix	391-394	4
α-helix	511-533	23
α-helix	535-536	2
α-helix	538-566	29

Chains B, D, F and H: 8 helices, 4 β-strands

Element	Residues	Length	Sheet
α-helix	8-20	13
β-strand	28	1	2
α-helix	30-39	10
α-helix	46-53	8
β-strand	64	1	2
α-helix	66-74	9
α-helix	80-92	13
β-strand	100-102	3	3
α-helix	103-112	10
α-helix	119-128	10
β-strand	136-138	3	3
α-helix	139-148	10

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Potassium voltage-gated channel subfamily KQT member 1	A, C, E, G	protein	545	Homo sapiens	P51787 (AlphaFold model)
Calmodulin-1	B, D, F, H	protein	149	Homo sapiens	P0DP23 (AlphaFold model)

Sequence of entity 1 (A, C, E, G), FASTA

>12DK_1 Potassium voltage-gated channel subfamily KQT member 1 (chains A, C, E, G)
ASDLGPRPPVSLDPRVSIYSTRRPVLARTHVQGRVYNFLERPTGWKCFVYHFAVFLIVLV
CLIFSVLSTCEQYAALATGTLFWMRIVLVVFFGTEYVVRLWSAGCRSKYVGLWGRLRFAR
KPISIIDLIVVVASMVVLCVGSKGQVFATSAIRGIEFLQILRMLHVDRQGGTWRLLGSVV
FIHRQELITTLYIGFLGLIFSSYFVYLAEKDAVNESGRVEFGSYADALWWGVVTVTTIGY
GDKVPQTWVGKTIASCFSVFAISFFALPAGILGSGFALKVQQKQRQKHFNRQIPAAASLI
QTAWRCYAAENPDSSTWKIYIRKAPRSHTLLSPSPKPKKSVVVKKKKFKLDKDNGVTPGE
KMLTVPHITCDPPEERRLDHFSVDGYDSSVRKSPTLLEVSMPHFMRTNSFAEDLDLEGET
LLTPITHISQLREHHRATIKVIRRMQYFVAKKKFQQARKPYDVRDVIEQYSQGHLNLMVR
IKELQRRLDQSIGKPSLFISVSEKSKDRGSNTIGARLNRVEDKVTQLDQRLALITDMLHQ
LLSLH

Sequence of entity 2 (B, D, F, H), FASTA

>12DK_2 Calmodulin-1 (chains B, D, F, H)
MADQLTEEQIAEFKEAFSLFDKDGDGTITTKELGTVMRSLGQNPTEAELQDMINEVDADG
NGTIDFPEFLTMMARKMKDTDSEEEIREAFRVFDKDGNGYISAAELRHVMTNLGEKLTDE
EVDEMIREADIDGDGQVNYEEFVQMMTAK

Ligands and cofactors

ID	Name	Formula	Copies
PT5	[(2R)-1-octadecanoyloxy-3-[oxidanyl-[(1R,2R,3S,4R,5R,6S)-2,3,6-tris(oxidanyl)-4…	C47 H85 O19 P3	4
CA	Calcium ion	Ca	8

Primary citation

PIP 2 activation of the cardiac I Ks potassium channel. Cui, J., Zhao, L., Xu, X. et al. Res Sq (2025). DOI 10.21203/rs.3.rs-7609003/v1 · PubMed

Other PDB entries of the same protein (UniProt P51787 (AlphaFold model), which also has an AlphaFold model), best resolution first:

3HFE 1.7 Å, A trimeric form of the Kv7.1 A domain Tail
3BJ4 2.0 Å, The KCNQ1 (Kv7.1) C-terminus, a multi-tiered scaffold for subunit assembly and protein…
7VVH 2.3 Å, Crystal Structure of the Kv7.1 C-terminal Domain in Complex with Calmodulin disease…
3HFC 2.45 Å, A trimeric form of the Kv7.1 A domain Tail, L602M/L606M mutant Semet
7XNN 2.5 Å, human KCNQ1-CaM-ML277-PIP2 complex in state B
9UJ4 2.59 Å, Structure of human KCNQ1-CaM complex
7XNK 2.6 Å, human KCNQ1-CaM in complex with ML277
7VUO 2.68 Å, Crystal Structure of the Kv7.1 C-terminal Domain in Complex with Calmodulin disease…
9VEC 2.7 Å, structure of human KCNQ1-KCNE1-CaM complex
4V0C 2.86 Å, Crystal Structure of the Kv7.1 proximal C-terminal Domain in Complex with Calmodulin
8SIK 2.9 Å, KCNQ1 with voltage sensor in the up conformation
9U7F 2.9 Å, structure of human KCNQ1-KCNE1-CaM complex

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