DNA processing by the MOBH family relaxase TraI encoded within the gonococcal genetic island.

摘要: Relaxases of the MOBH family are often found on large plasmids, genetic islands and integrative conjugative elements. Many members this contain an N-terminal relaxase domain (TraI_2) followed by a disordered middle part C-terminal unknown function (TraI_2_C). The TraI_2 contains two putative metal-binding motifs, HD motif alternative 3H motif. TraI, encoded within gonococcal island Neisseria gonorrhoeae, is prototype family. SAXS experiments showed that TraI_2_C form globular structures separated extended domain. cleaves oriT-ssDNA in site-specific Mn2+ or Co2+ dependent manner. minimal oriT encompasses 50 nucleotides, requires inverted repeat 3' nic-site several nucleotides around nic for efficient cleavage. Surprisingly, no stable covalent relaxase-DNA intermediate was observed. Mutagenesis conserved tyrosines cleavage abolished Y212A mutant, whereas Y212F Y212H mutants retained residual activity. motifs were essential residues D162 D267 metal ion binding. We propose active site binds ions, one high-affinity low-affinity site.