title: The solution structure of the C-terminal domain of TonB and interaction studies with TonB box peptides.
abstract: The TonB protein transduces energy from the proton gradient across the cytoplasmic membrane of Gram-negative bacteria to TonB-dependent outer membrane receptors. It is a critically important protein in iron uptake, and deletion of this protein is known to decrease virulence of bacteria in animal models. This system has been used for Trojan horse antibiotic delivery. Here, we describe the high-resolution solution structure of Escherichia coli TonB residues 103-239 (TonB-CTD). TonB-CTD is monomeric with an unstructured N terminus (103-151) and a well structured C terminus (152-239). The structure contains a four-stranded antiparallel beta-sheet packed against two alpha-helices and an extended strand in a configuration homologous to the C-terminal domain of the TolA protein. Chemical shift perturbations to the TonB-CTD (1)H-(15)N HSCQ spectrum titrated with TonB box peptides modeled from the E.coli FhuA, FepA and BtuB proteins were all equivalent, indicating that all three peptides bind to the same region of TonB. Isothermal titration calorimetry measurements demonstrate that TonB-CTD interacts with the FhuA-derived peptide with a K(D)=36(+/-7) microM. On the basis of chemical shift data, the position of Gln160, and comparison to the TolA gp3 N1 complex crystal structure, we propose that the TonB box binds to TonB-CTD along the beta3-strand.
authors.affiliation: Department of Biological Sciences, University of Calgary, 2500 University Drive N.W., Calgary, AB, Canada T2N 1N4.
authors.forename: R
authors.initials: R
authors.lastname: Sean Peacock
authors.forename: Aalim M
authors.initials: AM
authors.lastname: Weljie
authors.forename: S
authors.initials: S
authors.lastname: Peter Howard
authors.forename: Feodor D
authors.initials: FD
authors.lastname: Price
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Vogel
mesh_terms: D000595:Amino Acid Sequence; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012996:Solutions / Q000737:chemistry
chemical_list: D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D010446:Peptide Fragments; D012996:Solutions; C062093:tolA protein, E coli; C489181:tonB protein, E coli