W0209

Cadmium-induced Crystallization: Unusual [2Cd-4O] Cluster Formed to Bridge the Molecules. Chia-Kuei Wu^1,2, Bi-Cheng Wang¹ and John P. Rose¹, ¹Dept. of Biochemistry and Molecular Biology, Univ. of Georgia, Athens, GA 30602 and ²HIV Drug Resistance Program, National Cancer Institute, P.O. Box B, Frederick, MD 21702.

ALR (augmenter of liver regeneration) and its yeast homologs, ERV2p (essential for respiration and viability), are representatives of a eukaryotic family of sulfhydryl oxidases, which are capable of catalyzing disulfide bond formation for a number of proteins. ALR/ERV2p crystal structures contain a new five-helix-bundle fold for a noncovalently bound FAD (flavin adenine dinucleotide). The native ALR is crystallized in the condition containing 30% PEG 2000, 0.2 M MgCl₂, and Tris buffer pH 8.0. In an attempt of expressing his-tagged ALR to expedite the purification, the addition of his₆-tag to N-terminus of ALR has deterred the crystallization from native condition. The his₆-tagged crystals are obtained by varying the pH from 8.0 to 4.6 and the addition of cadmium divalent cations. The space group meanwhile changes from P2₁2₁2 to I4₁. In the 2.0 Å his-tagged ALR structure, cadmium cations form an unusual [2Cd-4O] cluster covalently links the symmetry-related homodimers through aspartic acids D74. In doing so, the local residues H74 and R58 change the orientation to accommodate the sizable cluster. Details will be presented in the poster.

Work is supported in part with funds from the Georgia Research Alliance, the University of Georgia Research Foundation and the National Cancer Institute.