Effects of Mercury on the Structure and Activity of BLM642-1290 Recombinant Helicase

ObjectiveBloom's syndrome is an autosomal recessive disorder characterized by genomic instability and a predisposition to many cancers. Mutations of the BLM gene (encoding a BLM helicase) may form a structure of the etiology of this disease. As a global pollutant, mercury poses a major threat to human health. The current study was conducted to elucidate the effects of Hg2+ on the structure and activity of BLM642-1290 recombinant helicase, and to further explore the molecular mechanisms of mercury toxicity to the DNA helicase.MethodsThe effects of Hg2+ on biological activity and structure of BLM642-1290 recombinant helicase were determined by fluorescence polarized, ultraviolet spectroscopic, and free-phosphorus assay technologies, respectively.ResultsThe helicase activity, the DNA-binding activity, and the ATPase activity of BLM642-1290 recombinant helicase were inhibited by Hg2+ treatment. The LMCT (ligand-to-metal charge transition) peaks of the helicase were enhanced with the increase of the Hg2+ level. The LMCT peaks of the same concentration of helicase gradually increased over time.ConclusionThe biological activity of BLM642-1290 recombinant helicase is inhibited by Hg2+ treatment. The conformation of the helicase is significantly altered by Hg2+. There exist two binding sites between Hg2+ and the helicase, which are located in the amino acid residues 1063-1066 and 940-944 of the helicase, respectively.