9BFC: Importin alpha-1/beta

Cryo-EM structure of importin alpha-1/beta bound to FG repeats. Determined by electron microscopy at 3.2 Å resolution. Released 10 Dec 2025.

Method: Electron microscopy
Resolution: 3.2 Å
Organisms: Saccharomyces cerevisiae, Homo sapiens
Chains: 5
Atoms: 7,383
Mol. weight: 105.6 kDa
Ligands: GLY, PHE
Released: 10 Dec 2025

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

Secondary structure: helices and β-sheets

9BFC contains 64 α-helices and 0 β-strands across 2 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 H: 61 helices, 0 β-strands

Element	Residues	Length
α-helix	3-11	9
α-helix	15-31	17
α-helix	33-45	13
α-helix	51-65	15
α-helix	70-81	12
α-helix	85-97	13
α-helix	109-120	12
α-helix	121-123	3
α-helix	129-138	10
α-helix	144-157	14
α-helix	163-166	4
α-helix	172-180	9
α-helix	188-200	13
α-helix	206-210	5
α-helix	212-222	11
α-helix	225-227	3
α-helix	232-247	16
α-helix	253-255	3
α-helix	256-260	5
α-helix	261-268	8
α-helix	273-302	30
α-helix	305-307	3
α-helix	319-329	11
α-helix	344-359	16
α-helix	360-362	3
α-helix	364-374	11
α-helix	380-392	13
α-helix	399-401	3
α-helix	403-416	14
α-helix	422-438	17
α-helix	441-444	4
α-helix	449-459	11
α-helix	464-488	25
α-helix	503-514	12
α-helix	521-523	3
α-helix	524-537	14
α-helix	541-543	3
α-helix	544-561	18
α-helix	565-567	3
α-helix	571-592	22
α-helix	597-600	4
α-helix	604-617	14
α-helix	623-639	17
α-helix	640-646	7
α-helix	647-659	13
α-helix	664-681	18
α-helix	682-688	7
α-helix	689-701	13
α-helix	707-709	3
α-helix	710-724	15
α-helix	726-728	3
α-helix	729-743	15
α-helix	752-777	26
α-helix	785-789	5
α-helix	791-793	3
α-helix	794-805	12
α-helix	812-828	17
α-helix	831-833	3
α-helix	834-837	4
α-helix	842-852	11
α-helix	856-874	19

Chain I: 3 helices, 0 β-strands

Element	Residues	Length
α-helix	9-12	4
α-helix	13-16	4
α-helix	24-51	28

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Phe-gly-ala	F	protein	3	Saccharomyces cerevisiae
Importin subunit beta-1	H	protein	876	Homo sapiens	Q14974 (AlphaFold model)
Importin subunit alpha-1	I	protein	53	Homo sapiens	P52292 (AlphaFold model)
Lys-pro-ala-phe-ser-phe-gly	J	protein	7	Saccharomyces cerevisiae
Ala-phe-ser-phe	C	protein	4	Saccharomyces cerevisiae

Sequence of entity 1 (F), FASTA

>9BFC_1 PHE-GLY-ALA (chains F)
FGA

Sequence of entity 2 (H), FASTA

>9BFC_2 Importin subunit beta-1 (chains H)
MELITILEKTVSPDRLELEAAQKFLERAAVENLPTFLVELSRVLANPGNSQVARVAAGLQ
IKNSLTSKDPDIKAQYQQRWLAIDANARREVKNYVLHTLGTETYRPSSASQCVAGIACAE
IPVNQWPELIPQLVANVTNPNSTEHMKESTLEAIGYICQDIDPEQLQDKSNEILTAIIQG
MRKEEPSNNVKLAATNALLNSLEFTKANFDKESERHFIMQVVCEATQCPDTRVRVAALQN
LVKIMSLYYQYMETYMGPALFAITIEAMKSDIDEVALQGIEFWSNVCDEEMDLAIEASEA
AEQGRPPEHTSKFYAKGALQYLVPILTQTLTKQDENDDDDDWNPCKAAGVCLMLLATCCE
DDIVPHVLPFIKEHIKNPDWRYRDAAVMAFGCILEGPEPSQLKPLVIQAMPTLIELMKDP
SVVVRDTAAWTVGRICELLPEAAINDVYLAPLLQCLIEGLSAEPRVASNVCWAFSSLAEA
AYEAADVADDQEEPATYCLSSSFELIVQKLLETTDRPDGHQNNLRSSAYESLMEIVKNSA
KDCYPAVQKTTLVIMERLQQVLQMESHIQSTSDRIQFNDLQSLLCATLQNVLRKVQHQDA
LQISDVVMASLLRMFQSTAGSGGVQEDALMAVSTLVEVLGGEFLKYMEAFKPFLGIGLKN
YAEYQVCLAAVGLVGDLCRALQSNIIPFCDEVMQLLLENLGNENVHRSVKPQILSVFGDI
ALAIGGEFKKYLEVVLNTLQQASQAQVDKSDYDMVDYLNELRESCLEAYTGIVQGLKGDQ
ENVHPDVMLVQPRVEFILSFIDHIAGDEDHTDGVVACAAGLIGDLCTAFGKDVLKLVEAR
PMIHELLTEGRRSKTNKAKTLARWATKELRKLKNQA

Sequence of entity 3 (I), FASTA

>9BFC_3 Importin subunit alpha-1 (chains I)
MSTNENANTPAARLHRFKNKGKDSTEMRRRRIEVNVELRKAKKDDQMLKRRNV

Sequence of entity 4 (J), FASTA

>9BFC_4 LYS-PRO-ALA-PHE-SER-PHE-GLY (chains J)
KPAFSFG

Sequence of entity 5 (C), FASTA

>9BFC_5 ALA-PHE-SER-PHE (chains C)
AFSF

Ligands and cofactors

ID	Name	Formula	Copies
GLY	Glycine	C2 H5 N O2	1
PHE	Phenylalanine	C9 H11 N O2	2

Primary citation

Ran modulates allosteric crosstalk between importin beta surfaces. Ko, Y.H., Li, F., Suinn, S.S. et al. Nat Commun (2025) 16:11425-11425. DOI 10.1038/s41467-025-66255-0 · PubMed

Other PDB entries of the same protein (UniProt Q14974 (AlphaFold model), which also has an AlphaFold model), best resolution first:

1IBR 2.3 Å, Complex of ran with importin beta
1QGR 2.3 Å, Structure of importin beta bound to the ibb domain of importin alpha (II crystal form,…
2P8Q 2.35 Å, Crystal Structure of human Importin beta bound to the Snurportin1 IBB-domain
1QGK 2.5 Å, Structure of importin beta bound to the ibb domain of importin alpha
3W5K 2.6 Å, Crystal structure of Snail1 and importin beta complex
9N85 2.6 Å, Cryo-EM structure of human importin beta:Ran-GTP:RanBP1 trimeric complex
1F59 2.8 Å, Importin-beta-fxfg nucleoporin complex
1O6O 2.8 Å, Importin Beta aa1-442 bound to five FxFG repeats from yeast Nsp1p. Second crystal form
1O6P 2.8 Å, Importin Beta bound to a GLFG Nucleoporin peptide
2QNA 2.84 Å, Crystal structure of human Importin-beta (127-876) in complex with the IBB-domain of…
1M5N 2.9 Å, Crystal structure of HEAT repeats (1-11) of importin b bound to the non-classical…
3LWW 3.15 Å, Structure of an open and closed conformation of Human Importin Beta bound to the…

Browse structure collections

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