Structural and genetic analyses of the RdgC protein in Escherichia coli.
Previous studies found that RdgC protein plays a role in the DNA repair system in Escherichia coli. In recBC sbcBC strains, loss of rdgC made growth of the strains dependent upon recombination, hence Recombination Dependent Growth. RdgC was also found to regulate the activity of RecA, a key protein in recombination, both in vivo and in vitro. The function of the protein, however, remains unknown. In this study, I purified and crystallised the RdgC protein. The crystal structure of the protein was then revealed as a homo-dimer, with a head to head, tail to tail organisation, resembling a ring structure. To further investigate how RdgC binds DNA and its in vivo functionality, point mutations and chunk deletions were designed and constructed; and I examined all the mutant proteins in DNA binding shift assays in vitro and in synthetic lethality assays in vivo. A DNA binding model was then proposed based on the results of the DNA binding shift assays. The mutant studies in vivo reinforce the idea that the DNA binding activity is crucial for RdgC's function in Escherichia coli.