A crystallographic analysis of the structure and function of 2,3-dihydroxybiphenyl 1,2-dioxygenase from Pseudomonas sp. LB400

Seungil Han, Purdue University

Abstract

The crystal structures of native and substrate-bound forms of 2,3-dihydroxybiphenyl 1,2-dioxygenase from Pseudomonas sp. LB400 have been determined under anaerobic conditions at 1.9A and 2.2A resolution, respectively. This non-heme ferrous iron containing extradiol dioxygenase catalyses the first ring opening step in biphenyl and PCB degradation. The crystal structure shows that the enzyme has N-terminal and C-terminal domains. The N-terminal and C-terminal domains are structurally similar, and there is topological symmetry within the domains as well. The Fe(II) center lies within a cylindrical active site cavity within the C-terminal domain. The iron is bound by three protein ligands (His$\sp{146}$, His$\sp{210}$, and Glu$\sp{260}$). The coordination geometry is square pyramidal; two equatorial positions are occupied by two water molecules, and the axial ligand is His$\sp{146}$. As the first high resolution structure of an extradiol dioxygenase, the structures of substrate-free and substrate-bound forms of 2,3-dihydroxybiphenyl 1,2-dioxygenase serve as a structural model for other members of the extradiol dioxygenase family and provide a framework for understanding the mechanism of the extradiol ring cleavage reactions.

Degree

Ph.D.

Advisors

Bolin, Purdue University.

Subject Area

Biophysics|Environmental engineering

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