W0257

Crystallization of the AhpC Component of the Alkyl Hydroperoxide Reductase Complex from Salmonella Typhimurium. Zachary A. Wood¹, Holly R. Ellis², Leslie B. Poole² and P. Andrew Karplus¹, ¹Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, NY 14853, USA, ²Department of Biochemistry, Wake Forest University Medical Center, Winston-Salem, North Carolina 27157, USA

The alkyl hydroperoxide reductase (AhpR) complex is involved in protecting many bacteria from oxidative damage. The AhpR complex consists of two proteins, AhpC and AhpF. AhpC is a homodimer of 22 kDa subunits with two intermolecular redox active disulfides. AhpF is a flavin dependent NADH oxidase that catalyzes the reduction of the AhpC disulfides, which in turn reduce alkyl hydroperoxides to H₂O and their corresponding alcohols. AhpC is a member of a large family of antioxidant enzymes, including the thiol-specific antioxidant enzyme (TSA) from mammals. No structures have been published for this family.

We have cloned, expressed and crystallized AhpC. The crystals belong to the monoclinic spacegroup P2₁: a=107, b=136, c=108 and [beta]=106.5. A native data set, complete to 2.5 Å resolution, has been collected at the Cornell High Energy Synchotron Source (CHESS). Protein in which the methionine residues have been replaced by selenomethionine has been crystallized for use in MAD phasing experiments.