title: Haloalkane dehalogenase LinB is responsible for beta- and delta-hexachlorocyclohexane transformation in Sphingobium indicum B90A.
abstract: Incubation of resting cells of Sphingobium indicum B90A, Sphingobium japonicum UT26, and Sphingobium francense Sp+ showed that they were able to transform beta- and delta-hexachlorocyclohexane (beta- and delta-HCH, respectively), the most recalcitrant hexachlorocyclohexane isomers, to pentachlorocyclohexanols, but only resting cells of strain B90A could further transform the pentachlorocyclohexanol intermediates to the corresponding tetrachlorocyclohexanediols. Moreover, experiments with resting cells of Escherichia coli expressing the LinB proteins of strains B90A, UT26, and Sp+ indicated that LinB was responsible for these transformations. Purified LinB proteins from all three strains also effected the formation of the respective pentachlorocyclohexanols. Although the three LinB enzymes differ only marginally with respect to amino acid sequence, they showed interesting differences with respect to substrate specificity. When LinB from strain B90A was incubated with beta- and delta-HCH, the pentachlorocyclohexanol products were further transformed and eventually disappeared from the incubation mixtures. In contrast, the LinB proteins from strains UT26 and Sp+ could not catalyze transformation of the pentachlorocyclohexanols, and these products accumulated in the incubation mixture. A mutant of strain Sp+ lacking linA and linB did not degrade any of the HCH isomers, including beta-HCH, and complementation of this mutant by linB from strain B90A restored the ability to degrade beta- and delta-HCH.
authors.affiliation: Department of Zoology, University of Delhi, Delhi 110007, India.
authors.forename: Poonam
authors.initials: P
authors.lastname: Sharma
authors.forename: Vishakha
authors.initials: V
authors.lastname: Raina
authors.forename: Rekha
authors.initials: R
authors.lastname: Kumari
authors.forename: Shweta
authors.initials: S
authors.lastname: Malhotra
authors.forename: Charu
authors.initials: C
authors.lastname: Dogra
authors.forename: Hansi
authors.initials: H
authors.lastname: Kumari
authors.forename: Hans-Peter E
authors.initials: HP
authors.lastname: Kohler
authors.forename: Hans-Rudolf
authors.initials: HR
authors.lastname: Buser
authors.forename: Christof
authors.initials: C
authors.lastname: Holliger
authors.forename: Rup
authors.initials: R
authors.lastname: Lal
mesh_terms: D001483:Base Sequence; D001673:Biodegradation, Environmental; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D004785:Environmental Pollutants / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D017353:Gene Deletion; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D001556:Hexachlorocyclohexane / Q000378:metabolism*; D006867:Hydrolases / Q000235:genetics / Q000378:metabolism*; D007306:Insecticides / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D042301:Sphingomonadaceae / Q000201:enzymology* / Q000235:genetics
chemical_list: D017931:DNA Primers; D004269:DNA, Bacterial; D004785:Environmental Pollutants; D007306:Insecticides; D011994:Recombinant Proteins; C086916:delta-hexachlorocyclohexane; D001556:Hexachlorocyclohexane; D006867:Hydrolases; C046137:haloalkane dehalogenase; C023888:beta-hexachlorocyclohexane