Transcriptional regulation of the cpr gene cluster in ortho-chlorophenol-respiring Desulfitobacterium dehalogenans

To characterize the expression and possible regulation of reductive dehalog enation in halorespiring bacteria, a 11.5-kb genomic fragment containing th e o-chlorophenol reductive dehalogenase-encoding cprBA genes of the gram-po sitive bacterium Desulfitobacterium dehalogenans was subjected to detailed molecular characterization. Sequence analysis revealed the presence of eigh t designated genes with the order cprTKZEBACD and with the same polarity ex cept for cprT. The deduced cprC and cprK gene products belong to the NirI/N osR and CRP-FNR families of transcription regulatory proteins, respectively . CprD and CprE are predicted to be molecular chaperones of the GroEL type, whereas cprT may encode a homologue of the trigger factor folding catalyst s, Northern blot analysis, reverse transcriptase PCR, and primer extension analysis were used to elucidate the transcriptional organization and regula tion of the cpr gene cluster. Results indicated halorespiration-specific tr anscriptional induction of the monocistronic cprT gene and the biscistronic cprBA and cprZE genes. Occasional read-through at cprC gives rise to a tet racistronic cprBACD transcript, Transcription of cprBA was induced 15-fold upon addition of the o-chlorophenolic substrate 3-chloro-4-hydroxyphenylace tic acid within 30 min with concomitant induction of dehalogenation activit y. Putative regulatory protein binding motifs that to some extent resemble the FNR box were identified in the cprT-cprK and cprK-cprZ intergenic regio ns and the promoter at cprB, suggesting a role for FNR-like CprK in the con trol of expression of the cprTKZEBACD genes.