Structural and mechanistic studies of Escherichia coli single-stranded DNA-binding protein interactions with genome maintenance enzymes

Bacterial single-strand (ss) DNA-binding proteins (SSBs) play essential protective and organizational roles in genome biology. To shield ssDNA from potential damage, SSBs bind tightly to ssDNA that arises during the course of DNA replication and repair. Far from being inert, ssDNA/SSB complexes in bacteria are active DNA processing centers where at least a dozen different enzymes gain access to genomic substrates by exploiting direct protein-protein interactions with SSB. In all cases examined to date, the last 8-10 residues of SSB's flexible C-terminus (SSB-Ct) form a docking site for heterologous proteins. How proteins bind to the SSB-Ct sequence and how these essential interactions affect the activities of genome maintenance enzymes are important aspects of genome biology. Moreover, given the essential nature of interactions with SSB, inhibitors that block association with SSB could provide novel avenues for antibiotic development.;In my Thesis, I describe advances that shed light on these aspects of bacterial genome biology. The first defines the physical basis underlying interaction between E. coli Exonuclease I (ExoI) and SSB through crystallographic and biochemical approaches (chapter 2). The second uses SSB peptide variants to identify roles for SSB C-terminal residues in ExoI/SSB complex formation (chapter 3). The third examines the activities of several small-molecule inhibitors that disrupt formation of ExoI/SSB complexes (and other SSB protein complexes) (chapter 4). Finally I conclude with several potential lines of investigation that could shed additional light on the important mechanisms that link bacterial SSBs to genome maintenance processes (chapter 5).