9N23: CIAP1-BIR3 with XB2 series SMAC mimetic ligand

Crystal structure of cIAP1-BIR3 with XB2 series SMAC mimetic ligand. Determined by X-ray diffraction at 1.8 Å resolution. Released 21 Jan 2026.

Method: X-ray diffraction
Resolution: 1.8 Å
Organism: Homo sapiens
Chains: 2
Atoms: 1,692
Mol. weight: 23.04 kDa
Ligands: A1BVC, ZN
Released: 21 Jan 2026

Explore 9N23 in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

9N23 contains 13 α-helices and 8 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: 6 helices, 4 β-strands

Element	Residues	Length	Sheet
α-helix	258-260	3
α-helix	263-268	6
α-helix	269-272	4
α-helix	281-286	6
β-strand	289-291	3	1
β-strand	294	1	2
β-strand	298-300	3	1
β-strand	306-307	2	1
α-helix	316-323	8
α-helix	328-344	17

Chain B: 7 helices, 4 β-strands

Element	Residues	Length	Sheet
α-helix	257-260	4
α-helix	263-268	6
α-helix	269-272	4
α-helix	281-286	6
β-strand	289-291	3	3
β-strand	298-300	3	3
β-strand	306-307	2	3
α-helix	316-323	8
β-strand	327	1	2
α-helix	328-334	7
α-helix	336-342	7

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Baculoviral IAP repeat-containing protein 2	A, B	protein	95	Homo sapiens	Q13490 (AlphaFold model)

Sequence of entity 1 (A, B), FASTA

>9N23_1 Baculoviral IAP repeat-containing protein 2 (chains A, B)
GSSISNLSMQTHAARMRTFMYWPSSVPVQPEQLASAGFYYVGRNDDVKCFCCDGGLRCWE
SGDDPWVEHAKWFPRCEFLIRMKGQEFVDEIQGRY

Ligands and cofactors

ID	Name	Formula	Copies
A1BVC	N-methyl-L-alanyl-3-methyl-L-valyl-N-(2-fluoro-5-methoxyphenyl)-L-prolinamide	C22 H33 F N4 O4	2
ZN	Zinc ion	Zn	2

Primary citation

Expanding the toolbox to develop IAP-based degraders of TEAD transcription factors. Gupta, N., Trainor, N., Radwan, M. et al. Commun Chem (2026) 9:69-69. DOI 10.1038/s42004-025-01871-x · PubMed

Other PDB entries of the same protein (UniProt Q13490 (AlphaFold model), which also has an AlphaFold model), best resolution first:

4HY4 1.25 Å, Crystal structure of cIAP1 BIR3 bound to T3170284
7QGJ 1.3 Å, Apo structure of BIR2 Domain of BIRC2
3D9T 1.5 Å, CIAP1-BIR3 in complex with N-terminal peptide from Caspase-9 (ATPFQE)
8DSF 1.5 Å, Structure of cIAP1 with BCCov
4KMN 1.52 Å, Structure of cIAP1-BIR3 and inhibitor
4LGE 1.55 Å, Crystal structure of clAP1 BIR3 bound to T3261256
6HPR 1.7 Å, Crystal structure of cIAP1 RING domain bound to UbcH5B-Ub and a non-covalent Ub
7TRL 1.74 Å, Crystal structure of human BIRC2 BIR3 domain in complex with histone H3
4HY5 1.75 Å, Crystal structure of cIAP1 BIR3 bound to T3256336
3UW4 1.79 Å, Crystal structure of cIAP1 BIR3 bound to GDC0152
4MU7 1.79 Å, Crystal structure of cIAP1 BIR3 bound to T3450325
5M6N 1.8 Å, Small Molecule inhibitors of IAP

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