The overall goal of this research proposal is to reveal the molecular function of RecN, a protein critical to the repair of DNA double-stranded breaks (DSBs) in bacteria. Bacterial RecN proteins share significant homology to the Structural Maintenance of Chromosomes (SMC) family of proteins. Eukaryotic SMC proteins have essential (although not fully understood) house keeping and tumor suppressor roles in a variety of DNA metabolic processes such as chromosomal condensation, sister chromatid cohesion and recombinational DNA repair. Although extensive genetic evidence underscores the importance of RecN proteins to bacterial genome maintenance, there has been no substantive biochemical investigation into their function and, consequently, the specific reactions requiring RecN have not been identified. This situation reflects the difficulties encountered in working with the Escherichia coli (a model bacterial organism) RecN protein by several research groups due to insolubility of the over-expressed protein. However, we have identified a RecN homolog that is soluble when expressed in E. coli and are positioned to initiate pilot studies to establish testable hypotheses for the biochemical function of bacterial RecN proteins in recombinational DNA repair pathways. This work will provide valuable models for understanding the molecular role that eukaryotic SMC proteins play in genome maintenance. PUBLIC HEALTH RELEVANCE: Biochemical approaches to provide valuable models for understanding the molecular role that SMC proteins play in genome maintenance and recombinational DNA repair.