Observation of the assembly of the nascent mineral core at the nucleation site of human mitochondrial ferritin

Bradley, Justin M., Bugg, Zinnia, Moore, Geoffrey R., Hemmings, Andrew M. and Le Brun, Nick E. (2025) Observation of the assembly of the nascent mineral core at the nucleation site of human mitochondrial ferritin. Journal of the American Chemical Society, 147 (16). 13699–13710. ISSN 0002-7863

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Abstract

Ferritins play a crucial role in iron homeostasis and detoxification in organisms from all kingdoms of life. They are composed of 24 α-helical subunits arranged around an interior cavity where an iron-containing mineral core can be reversibly stored. Despite decades of study, leading to significant progress in defining the routes of Fe2+ uptake and the mechanism of its subsequent oxidation to Fe3+ at diiron catalytic sites termed ferroxidase centers, the process of core synthesis from the product of ferroxidase center activity remains poorly understood. In large part, this is due to the lack of high-resolution structural data on ferritin cores anchored to their nucleation sites on the inner surface of the protein. Mitochondrial ferritins are atypical of those found in higher eukaryotes in that they are homopolymers in which all subunits contain both a ferroxidase center and a presumed but undefined core nucleation site. Here, in conjunction with a novel method for producing iron-enriched ferritin crystals, we exploit these unusual features to structurally characterize both the nucleation site of mitochondrial ferritin and a pentanuclear, ferrihydrite-like iron-oxo cluster formed there. Kinetic data for wild-type and variant proteins confirmed the functional importance of this site, indicating a critical role for E61 in the transfer of Fe3+ from the ferroxidase center to the nascent mineral core.

Item Type:	Article
Additional Information:	Data availability: Final coordinates and structure factors were deposited in the Protein Data Bank (https://www.rcsb.org) with accession codes 9EQ9 (FtMt 0 min O2), 9EQ8 (FtMt 2 min O2), 9EQA (FtMt 20 min O2), 9EQB (H57A/E61A/E64A FtMt 20 min O2), 9EQC (HuHF 20 min O2). Funding information: This work was supported by the UK’s Biotechnology and Biological Sciences Research Council through grants BB/I021884/1 and BB/R002363/1.
Faculty \ School:	Faculty of Science > School of Chemistry, Pharmacy and Pharmacology Faculty of Science Faculty of Science > School of Biological Sciences
UEA Research Groups:	Faculty of Science > Research Groups > Plant Sciences Faculty of Science > Research Groups > Molecular Microbiology Faculty of Science > Research Groups > Chemistry of Life Processes Faculty of Science > Research Centres > Centre for Molecular and Structural Biochemistry
Depositing User:	LivePure Connector
Date Deposited:	23 Apr 2025 14:30
Last Modified:	23 Apr 2025 14:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/99053
DOI:	10.1021/jacs.5c01337

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