Structure of the pcbC gene encoding 2,3-dihydroxybiphenyl dioxygenase of Pseudomonas sp. P20.

Pseudomonas sp. P20 is a soil bacterium growing in biphenyl or 4-chlorobiphenyl as the sole carbon and energy source, where the initial catabolism of biphenyl to form benzoate is catalyzed by four enzymes encoded in the pcbABCD gene cluster. The nucleotide sequence of the 2,3-dihydroxybiphenyl dioxygenase gene corresponding to the pcbC gene was determined. The pcbC gene was composed of 921 base pairs with an ATG initiation codon and a TGA termination codon, which can encode a polypeptide of molecular mass 34 kDa containing 306 amino acids. A promoter-like sequence and ribosome-binding sequence were identified upstream of the initiation codon. The deduced amino acid sequence of 2,3-dihydroxybiphenyl dioxygenase exhibited 47% identity with that of corresponding enzyme of Pseudomonas sp. DJ-12, and less than 35% identity with those of other extradiol-type dioxygenases.