title: Structural Basis of Novel Iron-Uptake Route and Reaction Intermediates in Ferritins from Gram-Negative Bacteria.
abstract: Iron and oxygen chemistry is mediated by iron proteins for many biological functions. Carboxylate-bridged diiron enzymes including ferritin have the common mechanism of oxygen activation via peroxodiferric intermediates. However, the route for iron uptake and the structural identification of intermediates still remain incomplete. The 4-fold symmetry channel of Helicobacter pylori ferritin was previously proposed as the iron-uptake route in eubacteria, but the amino acid residues at the 4-fold channel are not highly conserved. Here, we show evidence for a short path for iron uptake from His93 on the surface to the ferroxidase center in H. pylori ferritin and Escherichia coli ferritin. The amino acid residues along this path are highly conserved in Gram-negative bacteria and some archaea, and the mutants containing S20A and H93L showed significantly decreased iron oxidation. Surprisingly, the E. coli ferritin S20A crystal structure showed oxygen binding and side-on, symmetric μ-η2:η2peroxodiferric and oxodiferric intermediates. The results provide the structural basis for understanding the chemical nature of intermediates in iron oxidation in bacteria and some of archaea.
authors: Department of Biotechnology & Bioinformatics, Korea University, Sejong 339-700, Korea.
authors: Sella
authors: S
authors: Kim
authors: Department of Biotechnology & Bioinformatics, Korea University, Sejong 339-700, Korea.
authors: Ji-Hye
authors: JH
authors: Lee
authors: Department of Biotechnology & Bioinformatics, Korea University, Sejong 339-700, Korea.
authors: Jong Hyeon
authors: JH
authors: Seok
authors: Department of Biotechnology & Bioinformatics, Korea University, Sejong 339-700, Korea.
authors: Yi-Ho
authors: YH
authors: Park
authors: Department of Biotechnology & Bioinformatics, Korea University, Sejong 339-700, Korea.
authors: Sang Won
authors: SW
authors: Jung
authors: Department of Biotechnology & Bioinformatics, Korea University, Sejong 339-700, Korea.
authors: Art E
authors: AE
authors: Cho
authors: Functional Proteomics Center, Korea Institute of Science and Technology, Seoul 136-791, Korea.
authors: Cheolju
authors: C
authors: Lee
authors: Department of Food and Nutrition, Duksung Women's University, Seoul 132-714, Korea.
authors: Mi Sook
authors: MS
authors: Chung
authors: Department of Biotechnology & Bioinformatics, Korea University, Sejong 339-700, Korea. Electronic address: khkim@korea.ac.kr.
authors: Kyung Hyun
authors: KH
authors: Kim
mesh_terms: D019943:Amino Acid Substitution; D002570:Ceruloplasmin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004252:DNA Mutational Analysis; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D005293:Ferritins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016480:Helicobacter pylori / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation
chemical_list: D050505:Mutant Proteins; D005293:Ferritins; D007501:Iron; D002570:Ceruloplasmin
keywords: carboxylate-bridged diiron enzyme; ferritin; iron oxidation; iron uptake; peroxodiferric and oxodiferric intermediates