STRUCTURAL STUDIES OF DJ-1 FROM MULTIPLE EUKARYOTES

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Human DJ-1 plays an important role in the cellular response to oxidative stress, and certain point mutations in DJ-1 have been associated with rare forms of autosomal recessive early-onset Parkinson?s disease. In addition, DJ-1 was independently discovered as a ras-dependent oncogene and has been implicated in certain types of cancer. Studies by us and others have revealed that DJ-1 is a homodimer that contains a highly conserved cysteine residue with a depressed pKa value that is essential for DJ-1?s protective activity. Based on a previous atomic resolution structure of human DJ-1, we have made and crystallized a number of point mutants that alter the reactivity of this functionally critical cysteine residue in DJ-1. We propose to determine the X-ray crystal structures of these mutants in order to provide a clear structural explanation for our completed biochemical study of cysteine reactivity in DJ-1. The principal goal of the proposed work is to identify the structural determinants of cysteine reactivity in human DJ-1. In addition, we are undertaking the structural characterization of a new member of the DJ-1 superfamily from plants. Unlike all other characterized members of the DJ-1 superfamily, plant DJ-1 is predicted to be a pseudo-dimeric monomer with unique structural features. We will determine the X-ray crystal structure of a representative plant DJ-1 protein and use these results to form testable hypotheses about the function of plant DJ-1 proteins. These experiments are part of an ongoing effort to comprehensively characterize the function of eukaryotic DJ-1 from several different model organisms.