9E4A: Acid-sensing ion channel 1

Human ASIC1a at pH 8.5 with domain-swapped transmembrane domain. Determined by electron microscopy at 2.74 Å resolution. Released 21 Jan 2026.

Method: Electron microscopy
Resolution: 2.74 Å
Organism: Homo sapiens
Chains: 3
Atoms: 10,842
Mol. weight: 180.76 kDa
Released: 21 Jan 2026

Explore 9E4A in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

9E4A contains 81 α-helices and 63 β-strands across 3 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, B and C: 27 helices, 21 β-strands

Element	Residues	Length	Sheet
α-helix	18-24	7
α-helix	30-33	4
α-helix	41-69	29
β-strand	73-81	9	1
β-strand	85-86	2	2
α-helix	87-88	2
β-strand	89-94	6	3
α-helix	105-111	7
α-helix	132-141	10
α-helix	154-161	8
α-helix	163-164	2
α-helix	165-168	4
β-strand	169-174	6	4
β-strand	177-179	3	4
α-helix	181-183	3
β-strand	184-189	6	3
β-strand	192-197	6	3
α-helix	200-202	3
α-helix	205-207	3
β-strand	208-209	2	2
α-helix	214-216	3
β-strand	218-223	6	4
α-helix	226-228	3
α-helix	230-231	2
β-strand	245-250	6	3
β-strand	263-265	3	3
β-strand	269-275	7	4
β-strand	276-281	6	1
β-strand	291	1	5
α-helix	307-323	17
β-strand	326	1	6
α-helix	335	1
β-strand	336	1	6
α-helix	337-338	2
α-helix	339-341	3
α-helix	342-346	5
α-helix	347-355	9
α-helix	358-360	3
α-helix	364-365	2
β-strand	366	1	5
β-strand	368-373	6	1
β-strand	376-380	5	4
α-helix	384-394	11
α-helix	398-404	7
β-strand	405-412	8	4
β-strand	416-424	9	1
α-helix	428-442	15
α-helix	447-464	18

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Acid-sensing ion channel 1	A, B, C	protein	531	Homo sapiens	P78348 (AlphaFold model)

Sequence of entity 1 (A, B, C), FASTA

>9E4A_1 Acid-sensing ion channel 1 (chains A, B, C)
GGRMELKAEEEEVGGVQPVSIQAFASSSTLHGLAHIFSYERLSLKRALWALCFLGSLAVL
LCVCTERVQYYFHYHHVTKLDEVAASQLTFPAVTLCNLNEFRFSQVSKNDLYHAGELLAL
LNNRYEIPDTQMADEKQLEILQDKANFRSFKPKPFNMREFYDRAGHDIRDMLLSCHFRGE
VCSAEDFKVVFTRYGKCYTFNSGRDGRPRLKTMKGGTGNGLEIMLDIQQDEYLPVWGETD
ETSFEAGIKVQIHSQDEPPFIDQLGFGVAPGFQTFVACQEQRLIYLPPPWGTCKAVTMDS
DLDFFDSYSITACRIDCETRYLVENCNCRMVHMPGDAPYCTPEQYKECADPALDFLVEKD
QEYCVCEMPCNLTRYGKELSMVKIPSKASAKYLAKKFNKSEQYIGENILVLDIFFEVLNY
ETIEQKKAYEIAGLLGDIGGQMGLFIGASILTVLELFDYAYEVIKHKLCRRGKCQKEAKR
SSADKGVALSLDDVKRHNPCESLRGHPAGMTYAANILPHHPARGTFEDFTC

Primary citation

Conformational plasticity of human acid-sensing ion channel 1a. Cahill, J., Hartfield, K.A., Heusser, S.A. et al. Nat Struct Mol Biol (2026) 33:1171-1182. DOI 10.1038/s41594-026-01845-0 · PubMed

Other PDB entries of the same protein (UniProt P78348 (AlphaFold model), which also has an AlphaFold model), best resolution first:

9E4I 2.33 Å, Human ASIC1a at pH 7.5 in complex with MitTx
9E4H 2.61 Å, Human ASIC1a at pH 5.7 with rotated, domain-swapped transmembrane domain
9E4F 2.69 Å, Human ASIC1a at pH 5.7 with domain-swapped transmembrane domain
9E4K 2.77 Å, Human ASIC1a at pH 8.5, T26V mutation
9E4G 2.8 Å, Human ASIC1a at pH 5.7 with linear transmembrane domain
6L6N 2.86 Å, hASIC1a co-crystallized with Nafamostat
7RNN 2.86 Å, Human ASIC1a-Nb.C1 complex
9E4J 2.87 Å, Human ASIC1a at pH 6.5 in complex with MitTx
9E4B 3.09 Å, Human ASIC1a at pH 7.5 with domain-swapped transmembrane domain
9E4E 3.16 Å, Human ASIC1a at pH 6.5 with linear transmembrane domain
9E4D 3.19 Å, Human ASIC1a at pH 7.5 with linear transmembrane domain
6L6I 3.24 Å, hASIC1a co-crystallized with Mamb-1

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