title: Solution structure of Escherichia coli FeoA and its potential role in bacterial ferrous iron transport.
abstract: Iron is an indispensable nutrient for most organisms. Ferric iron (Fe(3+)) predominates under aerobic conditions, while during oxygen limitation ferrous (Fe(2+)) iron is usually present. The Feo system is a bacterial ferrous iron transport system first discovered in Escherichia coli K-12. It consists of three genes, feoA, feoB, and feoC (yhgG). FeoB is thought to be the main transmembrane transporter while FeoC is considered to be a transcriptional regulator. Using multidimensional nuclear magnetic resonance (NMR) spectroscopy, we have determined the solution structure of E. coli FeoA. The structure of FeoA reveals a Src-homology 3 (SH3)-like fold. The structure is composed of a β-barrel with two α-helices where one helix is positioned over the barrel. In comparison to the standard eukaryotic SH3 fold, FeoA has two additional α-helices. FeoA was further characterized by heteronuclear NMR dynamics measurements, which suggest that it is a monomeric, stable globular protein. Model-free analysis of the NMR relaxation results indicates that a slow conformational dynamic process is occurring in β-strand 4 that may be important for function. (31)P NMR-based GTPase activity measurements with the N-terminal domain of FeoB (NFeoB) indicate a higher GTP hydrolysis rate in the presence of potassium than with sodium. Further enzymatic assays with NFeoB suggest that FeoA may not act as a GTPase-activating protein as previously proposed. These findings, together with bioinformatics and structural analyses, suggest that FeoA may have a different role, possibly interacting with the cytoplasmic domain of the highly conserved core portion of the FeoB transmembrane region.
authors.affiliation: Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Alberta, Canada.
authors.forename: Cheryl K Y
authors.initials: CK
authors.lastname: Lau
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ishida
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Liu
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Vogel
mesh_terms: D001693:Biological Transport, Active / Q000502:physiology; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D004925:Escherichia / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D019906:Nuclear Magnetic Resonance, Biomolecular; D010088:Oxidoreductases / Q000378:metabolism*; D011487:Protein Conformation
chemical_list: D027682:Cation Transport Proteins; D029968:Escherichia coli Proteins; C470580:FeoB protein, E coli; D026901:Membrane Transport Proteins; C100775:feo protein, E coli; D010088:Oxidoreductases; C074859:iron oxidase, Thiobacillus ferrooxidans