3-DIMENSIONAL STRUCTURE OF 2,3-DIHYDROXYBIPHENYL DIOXYGENASE (BPHC ENZYME) FROM PSEUDOMONAS SP STRAIN-KKS102 HAVING POLYCHLORINATED BIPHENYL (PCB)-DEGRADING ACTIVITY

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 (resiudes 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 alpha-beta sandwich structure having a ''beta alpha beta beta beta'' 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.