<p>Ferritins are ubiquitous among life forms, as they are essential for iron homeostasis. Here, we unveiled a novel member of the ferritin family, baptised mini-bacterioferritin. The characterised mini-bacterioferritin was isolated from a microbial enrichment dominated by the methanotrophic archaeon ‘<i>Candidatus</i> Methanoperedens carboxydivorans’. Its atomic resolution crystal structure reveals a 12-mer assembly with a diiron ferroxidase centre located within a four-helix bundle. Redox-cycling experiments on protein crystals reveal a shift in iron position at the active site, which follows the established ferritin catalytic cycle. The 12-mer sphere-like structure harboured six Fe-coproporphyrin III ligands, positioned at the interdimeric interface, a characteristic previously only found in 24-mer bacterioferritins. Phylogenetics, together with structure predictions of closely related proteins, revealed that mini-bacterioferritins form a distinct clade within the ferritin family that might conserve ancestral traits. Future research will need to investigate the physiological roles of these enzymes, which were unsuspectingly widely distributed among prokaryotes.</p>

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Mini-bacterioferritins: structural insight into a ferritin-like protein from the anaerobic methane-oxidising archaeon Candidatus Methanoperedens carboxydivorans

  • Martijn Wissink,
  • Sylvain Engilberge,
  • Pedro Leão,
  • Robert S. Jansen,
  • Mike S. M. Jetten,
  • Mélissa Belhamri,
  • Olivier N. Lemaire,
  • Antoine Royant,
  • Cornelia U. Welte,
  • Tristan Wagner

摘要

Ferritins are ubiquitous among life forms, as they are essential for iron homeostasis. Here, we unveiled a novel member of the ferritin family, baptised mini-bacterioferritin. The characterised mini-bacterioferritin was isolated from a microbial enrichment dominated by the methanotrophic archaeon ‘Candidatus Methanoperedens carboxydivorans’. Its atomic resolution crystal structure reveals a 12-mer assembly with a diiron ferroxidase centre located within a four-helix bundle. Redox-cycling experiments on protein crystals reveal a shift in iron position at the active site, which follows the established ferritin catalytic cycle. The 12-mer sphere-like structure harboured six Fe-coproporphyrin III ligands, positioned at the interdimeric interface, a characteristic previously only found in 24-mer bacterioferritins. Phylogenetics, together with structure predictions of closely related proteins, revealed that mini-bacterioferritins form a distinct clade within the ferritin family that might conserve ancestral traits. Future research will need to investigate the physiological roles of these enzymes, which were unsuspectingly widely distributed among prokaryotes.