21IP: The MIDN Catch-IRF4 (A8C) fusion protein

The MIDN Catch-IRF4 (A8C) fusion protein. Determined by X-ray diffraction at 3.3 Å resolution. Released 4 Feb 2026.

Method: X-ray diffraction
Resolution: 3.3 Å
Organism: Homo sapiens
Chains: 2
Atoms: 978
Mol. weight: 15.2 kDa
Released: 4 Feb 2026

Explore 21IP in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

21IP contains 6 α-helices and 5 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 A: 3 helices, 3 β-strands

Element	Residues	Length	Sheet
α-helix	115-121	7
α-helix	126-132	7
β-strand	139-145	7	1
β-strand	148-156	9	1
α-helix	157	1
β-strand	166-174	9	1

Chain B: 3 helices, 2 β-strands

Element	Residues	Length	Sheet
β-strand	267-276	10	1
β-strand	279-287	9	1
α-helix	290-292	3
α-helix	303-317	15
α-helix	325-329	5

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Midnolin,Interferon regulatory factor 4	A	protein	68	Homo sapiens	Q15306 (AlphaFold model), Q504T8 (AlphaFold model)
Midnolin	B	protein	73	Homo sapiens	Q504T8 (AlphaFold model)

Sequence of entity 1 (A), FASTA

>21IP_1 Midnolin,Interferon regulatory factor 4 (chains A)
SRPEQSVMQALESLTETQVSDFLSGRSPLTLALRVGDHMMFVQLQLAWPACENGCQVTGT
FYCCAPPE

Sequence of entity 2 (B), FASTA

>21IP_2 Midnolin (chains B)
PGAVIESFVNHAPGVFSGTFSGTLHPNCQDSSGRPRRDIGTILQILNDLLSATRHYQGMP
PSLAQLRCHAGSG

Primary citation

Biochemical and structural studies of the midnolin Catch domain bound with both wild-type and mutant IRF4 peptides reveal the molecular basis for its broad substrate specificity. Zhong, Y., Chen, Z., Wang, G. et al. Acta Biochim Biophys Sin (Shanghai) (2026) 58:1235-1249. DOI 10.3724/abbs.2026002 · PubMed

Other PDB entries of the same protein (UniProt Q15306 (AlphaFold model), which also has an AlphaFold model), best resolution first:

6TD4 1.71 Å, IRF4 DNA-binding domain surface entropy mutant apo structure
9VEH 2.0 Å, The MIDN Catch-IRF4 (A8M) fusion protein
9TOY 2.1 Å, Investigating the binding mechanism of Interferon Regulatory Factor 4 to DNA in the…
9VE3 2.1 Å, The MIDN Catch-IRF4 (V2L) fusion protein
9VE7 2.15 Å, The MIDN Catch-IRF4 (A8V) fusion protein
7OOT 2.25 Å, X-ray Structure of Interferon Regulatory Factor 4 DNA binding domain bound to an…
7OGS 2.37 Å, X-ray Structure of Interferon Regulatory Factor 4 DNA binding domain bound to an…
7RH2 2.47 Å, IRF4 Transcription factor mutant -K59R
9CUG 2.49 Å, X-ray Structure of human Interferon Regulatory Factor 4 (IRF4) IAD Domain
9VE4 2.55 Å, The MIDN Catch-IRF4 fusion protein
7O56 2.6 Å, X-ray Structure of Interferon Regulatory Factor 4 DNA binding domain bound to an…
9VE6 2.8 Å, The MIDN Catch-IRF4 (F6Y) fusion protein

Browse structure collections

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