28NO: CTX/MthK complex

CTX/MthK complex. Determined by electron microscopy at 4.1 Å resolution. Released 26 Aug 2026.

Method: Electron microscopy
Resolution: 4.1 Å
Organisms: Leiurus hebraeus, Methanothermobacter thermautotrophicus str. Delta H
Chains: 5
Atoms: 3,084
Mol. weight: 157.92 kDa
Released: 26 Aug 2026

Explore 28NO in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

28NO contains 13 α-helices and 2 β-strands across 5 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: 3 helices, 0 β-strands

Element	Residues	Length
α-helix	21-42	22
α-helix	46-57	12
α-helix	70-105	36

Chain B: 3 helices, 0 β-strands

Element	Residues	Length
α-helix	21-42	22
α-helix	46-57	12
α-helix	70-107	38

Chain C: 3 helices, 0 β-strands

Element	Residues	Length
α-helix	21-40	20
α-helix	46-57	12
α-helix	70-104	35

Chain D: 3 helices, 0 β-strands

Element	Residues	Length
α-helix	21-41	21
α-helix	46-57	12
α-helix	70-104	35

Chain E: 1 helix, 2 β-strands

Element	Residues	Length	Sheet
β-strand	2	1	1
α-helix	10-16	7
β-strand	34	1	1

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Potassium channel toxin alpha-KTx 1.1	E	protein	37	Leiurus hebraeus	P13487 (AlphaFold model)
Calcium-gated potassium channel MthK	A, B, C, D	protein	344	Methanothermobacter thermautotrophicus str. Delta H	O27564 (AlphaFold model)

Sequence of entity 1 (E), FASTA

>28NO_1 Potassium channel toxin alpha-KTx 1.1 (chains E)
QFTNVSCTTSKECWSVCQRLHNTSRGKCMNKKCRCYS

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

>28NO_2 Calcium-gated potassium channel MthK (chains A, B, C, D)
MVLVIEIIRKHLPRVLKVPATRILLLVLAVIIYGTAGFHFIEGESWTVSLYWTFVTIATV
GYGDYSPSTPLGMYFTVTLIVLGIGTFAVAVERLLEFLINREQMKLMGLIDVAKSRHVVI
CGWSESTLECLRELRGSEVFVLAEDENVRKKVLRSGANFVHGDPTRVSDLEKANVRGARA
VIVDLESDSETIHCILGIRKIDESVRIIAEAERYENIEQLRMAGADQVISPFVISGRLMS
RSIDDGYEAMFVQDVLAEESTRRMVEVPIPEGSKLEGVSVLDADIHDVTGVIIIGVGRGD
ELIIDPPRDYSFRAGDIILGIGKPEEIERLKNYISALEENLYFQ

Primary citation

Atomic structure and plasticity of the CTX-MthK complex investigated by cryo-EM, NMR, and MD simulations. Qoraj, D., Mohr, S., Aldakul, Y.K. et al. Nat Commun (2026) 17. DOI 10.1038/s41467-026-76925-2 · PubMed

Other PDB entries of the same protein (UniProt P13487 (AlphaFold model), which also has an AlphaFold model), best resolution first:

4JTA 2.5 Å, Crystal structure of Kv1.2-2.1 paddle chimera channel in complex with Charybdotoxin
4JTD 2.54 Å, Crystal structure of Kv1.2-2.1 paddle chimera channel in complex with Lys27Met mutant of…
4JTC 2.56 Å, Crystal structure of Kv1.2-2.1 paddle chimera channel in complex with Charybdotoxin in Cs+
11DD 2.9 Å, Human Slo1-Charybdotoxin complex under divalent chelated condition
11DE 3.0 Å, Human Slo1-Charybdotoxin complex under divalent chelated condition - gating ring masked…
1BAH A two disulfide derivative of charybdotoxin with disulfide 13-33 replaced by two…
1CMR NMR solution structure of a chimeric protein, designed by transferring a functional…
2A9H NMR structural studies of a potassium channel / charybdotoxin complex
2CRD Analysis of side-chain organization on a refined model of charybdotoxin: structural and…

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