title: Characterization of pbt genes conferring increased Pb2+ and Cd2+ tolerance upon Achromobacter xylosoxidans A8.
abstract: The cluster of pbtTFYRABC genes is carried by plasmid pA81. Its elimination from Achromobacter xylosoxidans A8 resulted in increased sensitivity towards Pb(2+) and Cd(2+). Predicted pbtTRABC products share strong similarities with Pb(2+) uptake transporter PbrT, transcriptional regulator PbrR, metal efflux P1-ATPases PbrA and CadA, undecaprenyl pyrophosphatase PbrB and its signal peptidase PbrC from Cupriavidus metallidurans CH34. Expression of pbtABC or pbtA in a metal-sensitive Escherichia coli GG48 rendered the strain Pb(2+)-, Cd(2+)- and Zn(2+)-tolerant and caused decreased accumulation of the metal ions. Accumulation of Pb(2+), but not of Cd(2+) or Zn(2+), was promoted in E. coli expressing pbtT. Additional genes of the pbt cluster are pbtF and pbtY, which encode the cation diffusion facilitator (CDF)-like transporter and a putative fatty acid hydroxylase of unknown function, respectively. Expression of pbtF did not confer increased metal tolerance upon E. coli GG48, although the protein showed measurable Pb(2+)-efflux activity. Unlike the pbtT promoter, promoters of pbtABC, pbtF and pbtY contain features characteristic of promoters controlled by metal-responsive transcriptional regulators of the MerR family. Upregulation of pbtABC, pbtF and pbtY upon Pb(2+), Cd(2+) and Zn(2+) exposure was confirmed in wild-type Achromobacter xylosoxidans A8. Gel shift assays proved binding of purified PbtR to the respective promoters.
authors.affiliation: Department of Biochemistry and Microbiology, Institute of Chemical Technology, Prague, Technická 3, CZ-166 28 Prague, Czech Republic. Electronic address: katerina.hlozkova@vscht.cz.
authors.forename: Kateřina
authors.initials: K
authors.lastname: Hložková
authors.forename: Jáchym
authors.initials: J
authors.lastname: Suman
authors.forename: Hynek
authors.initials: H
authors.lastname: Strnad
authors.forename: Tomas
authors.initials: T
authors.lastname: Ruml
authors.forename: Vaclav
authors.initials: V
authors.lastname: Paces
authors.forename: Pavel
authors.initials: P
authors.lastname: Kotrba
mesh_terms: D042441:Achromobacter denitrificans / Q000187:drug effects* / Q000235:genetics; D002104:Cadmium / Q000633:toxicity*; D003001:Cloning, Molecular; D004361:Drug Tolerance; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics; D015870:Gene Expression; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005798:Genes, Bacterial; D007854:Lead / Q000633:toxicity*; D005810:Multigene Family; D010957:Plasmids
chemical_list: D002104:Cadmium; D007854:Lead
keywords: Achromobacter xylosoxidans; Cadmium; Lead; MerR family; Metal tolerance; P(1)-type ATPase; Transcriptional control; Zinc