title: Substrate-dependent expression of laccase in genetically modified Escherichia coli: design and construction of an inducible phenol-degrading system.
abstract: Phenolic compounds that are produced by variety of industrial and urban activities pose dangers to live organisms and the environment. Here, an inducible phenol-degrading system was designed and constructed in Escherichia coli as the host. CapR as a transcription activator in Pseudomonas species shows sensitivity towards most common phenolic pollutants. Upon presence of inducible pollutants and conformational changes of CapR, an inducible promoter will trigger the expression of a bacterial laccase gene, which had been isolated previously from a local Bacillus species. Laccase as a multicopper oxidase has the ability to oxidize wide variety of mono and polyphenols. The sensitivity of the inducible system was verified in the presence of phenol with the concentration range of 1 nM-10 mM. A linear correlation was observed between laccase expression and phenol concentration up to 1 mM. Laccase was expressed even in the lowest concentration of phenol (1 nM) after 2 hr of exposure. 2,2-Azinobis (3-ethylbenzthiazoline-6-sulfonate) (ABTS) as a mediator of laccase oxidative reactions could induce laccase expression through conformational changes of CapR. Recognition of ABTS by CapR not only results in expression of the remediating enzyme but also extends its substrate range to nonphenolic compounds.
authors.affiliation: Department of Genetics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran.
authors.forename: Mehrnoosh
authors.initials: M
authors.lastname: Fathi-Roudsari
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Behmanesh
authors.forename: Ali-Hatef
authors.initials: AH
authors.lastname: Salmanian
authors.forename: Majid
authors.initials: M
authors.lastname: Sadeghizadeh
authors.forename: Khosro
authors.initials: K
authors.lastname: Khajeh
mesh_terms: D001407:Bacillus / Q000201:enzymology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D052160:Benzothiazoles / Q000378:metabolism; D003001:Cloning, Molecular; D052918:Environmental Restoration and Remediation; D004789:Enzyme Activation; D057075:Enzyme Assays; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005809:Genes, Regulator; D042845:Laccase / Q000235:genetics / Q000378:metabolism*; D030781:Organisms, Genetically Modified / Q000235:genetics / Q000378:metabolism; D010084:Oxidation-Reduction; D019800:Phenol / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D013451:Sulfonic Acids / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D052160:Benzothiazoles; D011994:Recombinant Proteins; D013451:Sulfonic Acids; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; D019800:Phenol; D042845:Laccase