title: Structural characterization of encapsulated ferritin provides insight into iron storage in bacterial nanocompartments.
abstract: Ferritins are ubiquitous proteins that oxidise and store iron within a protein shell to protect cells from oxidative damage. We have characterized the structure and function of a new member of the ferritin superfamily that is sequestered within an encapsulin capsid. We show that this encapsulated ferritin (EncFtn) has two main alpha helices, which assemble in a metal dependent manner to form a ferroxidase center at a dimer interface. EncFtn adopts an open decameric structure that is topologically distinct from other ferritins. While EncFtn acts as a ferroxidase, it cannot mineralize iron. Conversely, the encapsulin shell associates with iron, but is not enzymatically active, and we demonstrate that EncFtn must be housed within the encapsulin for iron storage. This encapsulin nanocompartment is widely distributed in bacteria and archaea and represents a distinct class of iron storage system, where the oxidation and mineralization of iron are distributed between two proteins.
authors.affiliation: Institute of Quantitative Biology, Biochemistry and Biotechnology, School of Biological Sciences, The University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: Didi
authors.identifier: 0000-0002-3360-9352
authors.initials: D
authors.lastname: He
authors.affiliation: The School of Chemistry, The University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: Sam
authors.initials: S
authors.lastname: Hughes
authors.affiliation: The School of Chemistry, The University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: Sally
authors.initials: S
authors.lastname: Vanden-Hehir
authors.affiliation: Institute of Quantitative Biology, Biochemistry and Biotechnology, School of Biological Sciences, The University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: Atanas
authors.initials: A
authors.lastname: Georgiev
authors.affiliation: Institute of Quantitative Biology, Biochemistry and Biotechnology, School of Biological Sciences, The University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Altenbach
authors.affiliation: Institute for Cell and Molecular Biosciences, Newcastle University, Newcasle upon Tyne, United Kingdom.
authors.forename: Emma
authors.initials: E
authors.lastname: Tarrant
authors.affiliation: The School of Chemistry, The University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: C Logan
authors.initials: CL
authors.lastname: Mackay
authors.affiliation: Institute for Cell and Molecular Biosciences, Newcastle University, Newcasle upon Tyne, United Kingdom.
authors.forename: Kevin J
authors.identifier: 0000-0002-5577-7357
authors.initials: KJ
authors.lastname: Waldron
authors.affiliation: The School of Chemistry, The University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: David J
authors.identifier: 0000-0002-3741-2952
authors.initials: DJ
authors.lastname: Clarke
authors.affiliation: Institute of Quantitative Biology, Biochemistry and Biotechnology, School of Biological Sciences, The University of Edinburgh, Edinburgh, United Kingdom.|School of Biology, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Jon
authors.identifier: 0000-0002-9156-3284
authors.initials: J
authors.lastname: Marles-Wright
mesh_terms: D002570:Ceruloplasmin / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D005293:Ferritins / Q000737:chemistry* / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D011487:Protein Conformation; D055503:Protein Multimerization; D012247:Rhodospirillum rubrum / Q000201:enzymology* / Q000378:metabolism*
chemical_list: D005293:Ferritins; D007501:Iron; D002570:Ceruloplasmin
keywords: Rhodospirillum rubrum; biochemistry; biophysics; encapsulated ferritin; encapsulin; ferritin; structural biology