Crystal structure of dicamba monooxygenase: a Rieske nonheme oxygenase that catalyzes oxidative demethylation.

Razvan Dumitru, Wen Zhi Jiang, Donald P Weeks, Mark A Wilson

Department of Biochemistry, The University of Nebraska-Lincoln, Lincoln, NE 68588-0664, USA.

Journal of molecular biology 2009 Sep 18

filter terms:

Dicamba (3,6-dichloro-2-methoxybenzoic acid) is a widely used herbicide that is efficiently degraded by soil microbes. These microbes use a novel Rieske nonheme oxygenase, dicamba monooxygenase (DMO), to catalyze the oxidative demethylation of dicamba to 3,6-dichlorosalicylic acid (DCSA) and formaldehyde. We have determined the crystal structures of DMO in the free state, bound to its substrate dicamba, and bound to the product DCSA at 2.10-1.75 A resolution. The structures show that the DMO active site uses a combination of extensive hydrogen bonding and steric interactions to correctly orient chlorinated, ortho-substituted benzoic-acid-like substrates for catalysis. Unlike other Rieske aromatic oxygenases, DMO oxygenates the exocyclic methyl group, rather than the aromatic ring, of its substrate. This first crystal structure of a Rieske demethylase shows that the Rieske oxygenase structural scaffold can be co-opted to perform varied types of reactions on xenobiotic substrates.

Citation

Razvan Dumitru, Wen Zhi Jiang, Donald P Weeks, Mark A Wilson. Crystal structure of dicamba monooxygenase: a Rieske nonheme oxygenase that catalyzes oxidative demethylation. Journal of molecular biology. 2009 Sep 18;392(2):498-510