title: The plug domain of a neisserial TonB-dependent transporter retains structural integrity in the absence of its transmembrane beta-barrel.
abstract: Transferrin binding protein A (TbpA) is a TonB-dependent outer membrane protein expressed by pathogenic bacteria for iron acquisition from human transferrin. The N-terminal 160 residues (plug domain) of TbpA were overexpressed in both the periplasm and cytoplasm of Escherichia coli. We found this domain to be soluble and monodisperse in solution, exhibiting secondary structure elements found in plug domains of structurally characterized TonB-dependent transporters. Although the TbpA plug domain is apparently correctly folded, we were not able to observe an interaction with human transferrin by isothermal titration calorimetry or nitrocellulose binding assays. These experiments suggest that the plug domain may fold independently of the beta-barrel, but extracellular loops of the beta-barrel are required for ligand binding.
authors.affiliation: National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892-8030, USA.
authors.forename: M
authors.initials: M
authors.lastname: Oke
authors.forename: R
authors.initials: R
authors.lastname: Sarra
authors.forename: R
authors.initials: R
authors.lastname: Ghirlando
authors.forename: S
authors.initials: S
authors.lastname: Farnaud
authors.forename: A R
authors.initials: AR
authors.lastname: Gorringe
authors.forename: R W
authors.initials: RW
authors.lastname: Evans
authors.forename: S K
authors.initials: SK
authors.lastname: Buchanan
mesh_terms: D000818:Animals; D002942:Circular Dichroism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D009345:Neisseria meningitidis / Q000737:chemistry*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D033881:Transferrin-Binding Protein A / Q000737:chemistry* / Q000235:genetics
chemical_list: D033881:Transferrin-Binding Protein A