9HO6

Crystal Structure of the Human Frataxin protein in complex with a tailored Camelid Nanobody 16C10

Summary for 9HO6

• Entry DOI: 10.2210/pdb9ho6/pdb
• Descriptor: Frataxin mature form, Camelid Nanobody 16C10 (3 entities in total)
• Functional Keywords: complex, nanobody, mitochondrial regulation, friedreich ataxia, oxidoreductase
• Biological source: Homo sapiens (human); More
• Total number of polymer chains: 4
• Total formula weight: 57545.53

Authors

Garay-Alvarez, A.,Molina, R.,Hermoso, J.A. (deposition date: 2024-12-11, release date: 2025-12-24, Last modification date: 2026-07-08)

Primary citation

Pignataro, M.F.,Fernandez, N.B.,Garay-Alvarez, A.,Pavan, M.F.,Molina, R.,Munoz, I.G.,Grossi, J.,Noguera, M.,Vila, A.,Garcia, A.E.,Gentili, H.G.,Rodriguez, N.A.,Aran, M.,Parreno, V.,Bok, M.,Hermoso, J.A.,Ibanez, L.I.,Santos, J.
Nanobodies as tools for studying human frataxin biology.
Commun Biol, 9:181-181, 2026

PubMed Abstract: Iron-sulfur clusters are essential cofactors for the accurate cellular function of many proteins. In eukaryotic cells, the biogenesis of most iron-sulfur clusters occurs in the mitochondria and involves the action of the Cys desulfurase supercomplex, which is activated by the protein frataxin (FXN). The decrease of FXN expression and/or function results in Friedreich's ataxia (FRDA).In this work, several nanobodies specific to human FXN were selected via phage display, demonstrating a wide range of effects on Cys desulfurase activity and a strong interaction with FXN. Nanobody interaction stabilized wild-type and FRDA-related FXN variants in vitro. FXN-nanobody complexes were characterized by NMR, SAXS, and X-ray crystallography. Additionally, Nanobody expression was studied in human cells. The subcellular localization, direct interaction with FXN by in situ proximity ligation assay, effect on cell viability, Fe-S-dependent enzymatic activities, and oxygen consumption rates were analyzed. Significantly, nanobody expression did not alter these key metabolic variables, suggesting that the interaction with FXN did not disrupt the pathway.As a whole, our results suggest that nanobodies can serve as binding partners for mitochondrial FXN. However, the specific effect of the nanobodies on the conformational stability of FRDA-related FXN variants in cells should be investigated.

PubMed: 41484353
DOI: 10.1038/s42003-025-09458-x

Experimental method

X-RAY DIFFRACTION (2 Å)