FIG 7.

(A) DprA-mediated loading of RecA on ssDNA. DprA_Sp dimer (C-C term) forms a nucleoprotein complex with ssDNA. DprA_Sp dimer bound to ssDNA offers the best suitable platform for RecA nucleation. After ssDNA binding of DprA_Sp dimer conformation change takes place, and sites of DprA_Sp-RecA interaction open up (EDE triad of DprA_Sp interacts with RRK triad of RecA). Once DprA_Sp-RecA interaction is established, DprA_Sp is converted to a monomer. This change allows RecA loading on ssDNA, followed by RecA nucleation, continued polymerization, and DprA_Sp leaving the ssDNA. (B) Residues important for S. pneumoniae DprA protein DNA binding and dimerization. Five lysine (K119/K144/K175/K202/K225) residues on the basic face of DprA_Sp are essential for DNA binding activity. DNA binding activity is completely abolished when lysine is mutated to alanine, whereas the partial patch mutation 3KA and 2KA produces a similar effect equal to that of R115A single mutant. This basic patch is localized opposite the RecA binding site.