CRYSTAL-STRUCTURE OF THE BIPHENYL-CLEAVING EXTRADIOL DIOXYGENASE FROMA PCB-DEGRADING PSEUDOMONAD

Polychlorinated biphenyls (PCBs) typify a class of stable aromatic pol lutants that are targeted by bioremediation strategies. In the aerobic degradation of biphenyl by bacteria, the key step of ring cleavage is catalyzed by an Fe(II)-dependent extradiol dioxygenase. The crystal s tructure of 2,3-dihydroxybiphenyl 1,2-dioxygenase from a PCB-degrading strain of Pseudomonas cepacia has been determined at 1.9 angstrom res olution, The monomer comprises amino- and carboxyl-terminal domains, S tructural homology between and within the domains reveals evolutionary relationships within the extradiol dioxygenase family. The iron atom has five ligands in square pyramidal geometry: one glutamate and two h istidine side chains, and two water molecules.