The hdhA gene encodes a haloacid dehalogenase that is regulated by the LysR-type regulator, HdhR, in Sinorhizobium meliloti.
The plasmid pSymA, in the nitrogen-fixing soil bacterium, Sinorhizobium meliloti, carries a 750-bp ORF (SMa1978) designated, hdhA, which encodes a novel dehalogenase that can detoxify haloacid compounds, showing a preference for haloacetic acids. Purified His-tagged HdhA demonstrated the apparent ability to dehalogenate chloroacetic acid and trifluoroacetic acid. In addition, upstream of hdhA, a gene encoding a lysR-type transcription regulator denoted, hdhR (SMa1979), has been identified to be a transcriptional repressor of hdhA expression. In an hdhR knockout mutant, hdhA promoter activity was markedly increased. Purified 32-kDa His-tagged HdhR repressed expression of hdhA by specifically binding to the promoter region of hdhA, as demonstrated by gel mobility shift assay and DNase I foot printing experiments. Moreover, the pesticide, pentachlorophenol, was also found to induce hdhA expression via HdhR. Site-directed mutants, in which the Cys residues at positions 160 and 192 in HdhR were changed to Ser, were constructed. C160S and C192S single mutants showed diminished HdhR-mediated repression of hdhA expression, while a C160S:C192S double mutant could no longer repress expression of hdhA.
Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok, Thailand.
Ratiboot
R
Sallabhan
Jarunee
J
Kerdwong
James M
JM
Dubbs
Kumpanart
K
Somsongkul
Wirongrong
W
Whangsuk
Phairin
P
Piewtongon
Skorn
S
Mongkolsuk
Suvit
S
Loprasert
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D018983:DNA Footprinting / Q000379:methods; D015964:Gene Expression Regulation, Bacterial; D006867:Hydrolases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D016415:Sequence Alignment; D016962:Sinorhizobium meliloti / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D014157:Transcription Factors; D006867:Hydrolases; C034507:2-haloacid dehalogenase