title: X-ray crystallography and isothermal titration calorimetry studies of the Salmonella zinc transporter ZntB.
abstract: The ZntB Zn(2+) efflux system is important for maintenance of Zn(2+) homeostasis in Enterobacteria. We report crystal structures of ZntB cytoplasmic domains from Salmonella enterica serovar Typhimurium (StZntB) in dimeric and physiologically relevant homopentameric forms at 2.3 Å and 3.1 Å resolutions, respectively. The funnel-like structure is similar to that of the homologous Thermotoga maritima CorA Mg(2+) channel and a Vibrio parahaemolyticus ZntB (VpZntB) soluble domain structure. However, the central α7 helix forming the inner wall of the StZntB funnel is oriented perpendicular to the membrane instead of the marked angle seen in CorA or VpZntB. Consequently, the StZntB funnel pore is cylindrical, not tapered, which may represent an "open" form of the ZntB soluble domain. Our crystal structures and isothermal titration calorimetry data indicate that there are three Zn(2+) binding sites in the full-length ZntB, two of which could be involved in Zn(2+) transport.
authors.affiliation: Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4965, USA.
authors.forename: Qun
authors.initials: Q
authors.lastname: Wan
authors.forename: Md Faiz
authors.initials: MF
authors.lastname: Ahmad
authors.forename: James
authors.initials: J
authors.lastname: Fairman
authors.forename: Bonnie
authors.initials: B
authors.lastname: Gorzelle
authors.forename: María
authors.initials: M
authors.lastname: de la Fuente
authors.forename: Chris
authors.initials: C
authors.lastname: Dealwis
authors.forename: Michael E
authors.initials: ME
authors.lastname: Maguire
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D002151:Calorimetry; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D027682:Cation Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D004926:Escherichia coli; D017136:Ion Transport; D008958:Models, Molecular; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012480:Salmonella Infections / Q000821:virology; D012486:Salmonella typhimurium / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020124:Thermotoga maritima / Q000737:chemistry / Q000378:metabolism; D014736:Vibrio parahaemolyticus / Q000737:chemistry / Q000378:metabolism; D015032:Zinc / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D011994:Recombinant Proteins; C017800:zinc-binding protein; D015032:Zinc