Natural transformation in bacteria is a horizontal gene transfer mechanism that allows exogenous DNA internalization and integration into the bacterial genome. The uptake of double-stranded DNA (dsDNA) from the outer environment is followed by the conversion of dsDNA to single-stranded DNA (ssDNA) and its transport into the cytoplasm (Mortier-Barrière et al., 2007). The transforming ssDNA is proposed to be bound and protected from the cytoplasmic nucleases by DprA (for DNA processing protein A) (Dwivedi et al., 2013). DprA is a ubiquitous protein in bacteria that has a key role in natural transformation process (Ando et al., 1999). In most bacteria, DprA is divided into three domains: a N-terminal domain, a conserved central domain and a C-terminal domain. In Helicobacter pylori, DprA (HpDprA) possesses only the central and the C-terminal domains (Ando et al., 1999). Functional analysis of HpDprA highlights the essential role of C-terminal domain in H. pylori natural transformation process.
In order to find the function of C-terminal domain in natural transformation process, an analysis of HpDprA’s 3D structure was performed. This structure result of the data compilation arising from the X-ray structure of the central domain dimer, the NMR structure of the C-terminal domain, and the structure of the full-length DprA dimer obtained in solution by SAXS. Putative interaction sites between HpDprA and DNA were identified. Using a site directed mutagenesis approach, several mutants of HpDprA were generated. Electrophoretic Mobility Shift Assay shows that the isolated C-terminal domain is not able to interact neither with ssDNA nor dsDNA, although its structural homology to winged helix DNA binding motifs. In contrast, the key residues of the central domain are crucial for both interactions. The cellular function of the C-terminal of HpDprA stays to be elucidated.