9HO4: Human Frataxin protein

Crystal Structure of the Human Frataxin protein in complex with a tailored Camelid Nanobody 6B1. Determined by X-ray diffraction at 1.76 Å resolution. Released 24 Dec 2025.

Method: X-ray diffraction
Resolution: 1.76 Å
Organisms: Homo sapiens, Lama glama
Chains: 2
Atoms: 2,042
Mol. weight: 26.59 kDa
Released: 24 Dec 2025

Explore 9HO4 in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

9HO4 contains 7 α-helices and 20 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: 2 helices, 8 β-strands

Element	Residues	Length	Sheet
α-helix	5-24	20
β-strand	31	1	1
β-strand	35-39	5	2
β-strand	42-46	5	2
β-strand	53-59	7	2
β-strand	64-69	6	2
β-strand	73-79	7	2
β-strand	84-86	3	2
β-strand	91-92	2	2
α-helix	93-105	13

Chain C: 5 helices, 12 β-strands

Element	Residues	Length	Sheet
β-strand	4-7	4	3
β-strand	10-12	3	1
β-strand	18-24	7	3
α-helix	26-29	4
β-strand	33-39	7	1
β-strand	46-52	7	1
β-strand	59-62	4	1
β-strand	70-75	6	3
β-strand	80-85	6	3
α-helix	90-92	3
β-strand	94-100	7	1
α-helix	103-104	2
β-strand	105	1	4
α-helix	110	1
β-strand	111	1	4
α-helix	112	1
β-strand	117-121	5	1

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Frataxin mature form	A	protein	114	Homo sapiens	Q16595 (AlphaFold model)
Camelid Nanobody 6B1	C	protein	128	Lama glama

Sequence of entity 1 (A), FASTA

>9HO4_1 Frataxin mature form (chains A)
TTYERLAEETLDSLAEFFEDLADKPYTFEDYDVSFGSGVLTVKLGGDLGTYVINKQTPNK
QIWLSSPSSGPKRYDWTGKNWVYSHDGVSLHELLAAELTKALKTKLDLSSLAYS

Sequence of entity 2 (C), FASTA

>9HO4_2 Camelid Nanobody 6B1 (chains C)
VQLQESGGGLVQPGGSLRLSCAASGSIFSTDAMGWYRQFPGKNRKLVARISSGDYGDYTN
YADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCNSVPPAPGEYGRDYWGAGTQVTV
SSAAAYPY

Primary citation

Nanobodies as tools for studying human frataxin biology. Pignataro, M.F., Fernandez, N.B., Garay-Alvarez, A. et al. Commun Biol (2026) 9:181-181. DOI 10.1038/s42003-025-09458-x · PubMed

Other PDB entries of the same protein (UniProt Q16595 (AlphaFold model), which also has an AlphaFold model), best resolution first:

3T3L 1.15 Å, 1.15 A structure of human frataxin variant Q153A
3T3K 1.24 Å, 1.24 A Structure of Friedreich's ataxia frataxin variant Q148R
3S4M 1.3 Å, Crystal structure of wild-type human frataxin
3S5E 1.31 Å, Crystal structure of human frataxin variant W155R, one of the Friedreich's ataxia point…
3T3T 1.38 Å, 1.38 A structure of human frataxin variant Q148G
3S5D 1.5 Å, Crystal structure of human frataxin variant W155A
3S5F 1.5 Å, Crystal structure of human frataxin variant W155F
9HO5 1.5 Å, Crystal Structure of the Human Frataxin protein in complex with a tailored Camelid…
3T3X 1.57 Å, 1.57 A structure of Friedreich's ataxia frataxin variant R165C
3T3J 1.7 Å, 1.70 A structure of Friedreich's ataxia frataxin variant N146K
1EKG 1.8 Å, Mature human frataxin
9HO6 2.0 Å, Crystal Structure of the Human Frataxin protein in complex with a tailored Camelid…

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