title: The crystal structure of ferritin from Chlorobium tepidum reveals a new conformation of the 4-fold channel for this protein family.
abstract: Ferritins are ubiquitous iron-storage proteins found in all kingdoms of life. They share a common architecture made of 24 subunits of five α-helices. The recombinant Chlorobium tepidum ferritin (rCtFtn) is a structurally interesting protein since sequence alignments with other ferritins show that this protein has a significantly extended C-terminus, which possesses 12 histidine residues as well as several aspartate and glutamic acid residues that are potential metal ion binding residues. We show that the macromolecular assembly of rCtFtn exhibits a cage-like hollow shell consisting of 24 monomers that are related by 4-3-2 symmetry; similar to the assembly of other ferritins. In all ferritins of known structure the short fifth α-helix adopts an acute angle with respect to the four-helix bundle. However, the crystal structure of the rCtFtn presented here shows that this helix adopts a new conformation defining a new assembly of the 4-fold channel of rCtFtn. This conformation allows the arrangement of the C-terminal region into the inner cavity of the protein shell. Furthermore, two Fe(III) ions were found in each ferroxidase center of rCtFtn, with an average FeA-FeB distance of 3 Å; corresponding to a diferric μ-oxo/hydroxo species. This is the first ferritin crystal structure with an isolated di-iron center in an iron-storage ferritin. The crystal structure of rCtFtn and the biochemical results presented here, suggests that rCtFtn presents similar biochemical properties reported for other members of this protein family albeit with distinct structural plasticity.
authors: Centro de Bioinformática y Simulación Molecular, Facultad de Ingeniería, Universidad de Talca, Talca, Chile.
authors: Mauricio
authors: M
authors: Arenas-Salinas
authors: Department of Chemistry & School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, UK.
authors: Philip D
authors: PD
authors: Townsend
authors: Centro de Bioinformática y Biología Integrativa, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Santiago, Chile.
authors: Christian
authors: C
authors: Brito
authors: Centro de Bioinformática y Biología Integrativa, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Santiago, Chile.
authors: Valeria
authors: V
authors: Marquez
authors: Centro de Bioinformática y Biología Integrativa, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Santiago, Chile.
authors: Vanessa
authors: V
authors: Marabolli
authors: Centro de Bioinformática y Biología Integrativa, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Santiago, Chile.
authors: Fernando
authors: F
authors: Gonzalez-Nilo
authors: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA.
authors: Cata
authors: C
authors: Matias
authors: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA.
authors: Richard K
authors: RK
authors: Watt
authors: Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Granada, Granada, Spain.
authors: Juan D
authors: JD
authors: López-Castro
authors: Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Granada, Granada, Spain.
authors: José
authors: J
authors: Domínguez-Vera
authors: Department of Chemistry & School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, UK.
authors: Ehmke
authors: E
authors: Pohl
authors: Departamento de Química Física, Facultad de Química, Pontificia Universidad Católica de Chile, Santiago, Chile. Electronic address: ayevenes@uc.cl.
authors: Alejandro
authors: A
authors: Yévenes
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D041883:Chlorobium / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D005293:Ferritins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D056004:Molecular Dynamics Simulation; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D021122:Protein Subunits; D011994:Recombinant Proteins; D005293:Ferritins
keywords: Bacterial ferritin; Crystal structure; Ferroxidase center; HAADF-STEM