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: The three-dimensional structure of an enzyme, 2,3-dihydroxybiphenyl dioxygenase, from Pseudomonas sp. strain KKS102 has been solved by X-ray crystal structure analysis. The enzyme conventionally called "BphC" is an important member in the biodegradation pathway for PCBs (polychlorinated biphenyls) which are the widely distributed environmental pollutants. The BphC enzyme is an oligomeric enzyme made up of eight identical subunits of 292 amino acid residues. Each subunit consists of two domains: Domain 1(residues 1 to 135) and Domain 2 (resiuues 136 to 292). Each domain consists of two repetitions of a unique folding motif each consisting of ca. 55 amino acid residues. The unique motif may be classified into an a'/3 sandwich structure having a "/3a43f3/3" type topology. In the active site of each subunit, one Fe ion surrounded by five ligands roughly arranged in a trigonal bipyramidal geometry was found.

Crystals have been obtained for a 2,3-dihydroxybiphenyl dioxygenase (conventionally called BphC) from a polychlorinated biphenyl (PCB)-degrader, Pseudomonas sp. strain KKS102. The crystals were grown using both ammonium sulfate and MPD as the precipitating agents. The crystals belonged to a tetragonal space group (I422) and diffracted to 2.5 A.

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