title: Trichloroethene reductive dehalogenase from Dehalococcoides ethenogenes: sequence of tceA and substrate range characterization.
abstract: The anaerobic bacterium Dehalococcoides ethenogenes is the only known organism that can completely dechlorinate tetrachloroethene or trichloroethene (TCE) to ethene via dehalorespiration. One of two corrinoid-containing enzymes responsible for this pathway, TCE reductive dehalogenase (TCE-RDase) catalyzes the dechlorination of TCE to ethene. TCE-RDase dehalogenated 1,2-dichloroethane and 1, 2-dibromoethane to ethene at rates of 7.5 and 30 micromol/min/mg, respectively, similar to the rates for TCE, cis-dichloroethene (DCE), and 1,1-DCE. A variety of other haloalkanes and haloalkenes containing three to five carbon atoms were dehalogenated at lower rates. The gene encoding TCE-RDase, tceA, was cloned and sequenced via an inverse PCR approach. Sequence comparisons of tceA to proteins in the public databases revealed weak sequence similarity confined to the C-terminal region, which contains the eight-iron ferredoxin cluster binding motif, (CXXCXXCXXXCP)(2). Direct N-terminal sequencing of the mature enzyme indicated that the first 42 amino acids constitute a signal sequence containing the twin-arginine motif, RRXFXK, associated with the Sec-independent membrane translocation system. This information coupled with membrane localization studies indicated that TCE-RDase is located on the exterior of the cytoplasmic membrane. Like the case for the two other RDases that have been cloned and sequenced, a small open reading frame, tceB, is proposed to be involved with membrane association of TCE-RDase and is predicted to be cotranscribed with tceA.
authors.affiliation: Battelle/Pacific Northwest National Laboratory, Richland, Washington 99352, USA. jon.magnuson@pnl.gov
authors.forename: J K
authors.initials: JK
authors.lastname: Magnuson
authors.forename: M F
authors.initials: MF
authors.lastname: Romine
authors.forename: D R
authors.initials: DR
authors.lastname: Burris
authors.forename: M T
authors.initials: MT
authors.lastname: Kingsley
mesh_terms: D000595:Amino Acid Sequence; D001421:Bacteria, Anaerobic / Q000201:enzymology* / Q000235:genetics*; D001483:Base Sequence; D001673:Biodegradation, Environmental; D017931:DNA Primers / Q000235:genetics; D005798:Genes, Bacterial; D006846:Hydrocarbons, Halogenated / Q000378:metabolism; D006867:Hydrolases / Q000235:genetics* / Q000378:metabolism*; D008566:Membranes / Q000201:enzymology; D008969:Molecular Sequence Data; D010088:Oxidoreductases; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D017931:DNA Primers; D006846:Hydrocarbons, Halogenated; D010088:Oxidoreductases; C112990:tetrachloroethene dehalogenase; D006867:Hydrolases