Structure of RecJ exonuclease defines its specificity for single-stranded DNA

摘要: RecJ is a single-stranded DNA (ssDNA)-specific 5′-3′ exonuclease that plays an important role in repair and recombination. To elucidate how achieves its high specificity for ssDNA, we determined the entire structures of both ligand-free form complex with Mn2+ or Mg2+ by x-ray crystallography. The consists four domains molecule O-like structure. One two newly identified had structural similarities to oligonucleotide/oligosaccharide-binding (OB) fold. OB fold domain alone could bind DNA, indicating this novel member superfamily. truncated containing only core exhibited much lower affinity ssDNA substrate compared intact RecJ. These results support hypothesis these features allow specific binding ssDNA. In addition, structure RecJ-Mn2+ suggests hydrolysis reaction catalyzed proceeds through two-metal ion mechanism.