Structural analysis of a conjugative relaxosome by SAXS

Antibiotic resistance is emerging as a major threat to human health. This proposal aims to deepen our understanding of bacterial conjugation, the primary mechanism responsible for the spread of antibiotic resistance genes. In the conjugative process, a single DNA strand of the plasmid is transferred through a Type IV secretion system bound to a relaxase protein (TrwC in R388 plasmid). Prior to transfer, a macromolecular complex comprising the relaxase TrwC, the plasmid DNA, and accessory proteins TrwA and IHF (integration host factor) is assembled. This complex, termed “relaxosome”, must interact with the secretion channel to initiate substrate transfer. To date, no structural information is available regarding the relaxosome itself or the mechanism by which it interacts with the secretion channel. We have successfully assembled the relaxosome complex in vitro. Gaining structural insights of this complex by SAXS will allow us a comprehensive understanding of the conjugative process.