Improvement of duplex-specific nuclease salt tolerance by fusing DNA-binding domain of DNase from an extremely halotolerant bacterium Thioalkalivibrio sp. K90mix

Salt tolerance is an important property of duplex-specific nuclease (DSN). DSN with high salt tolerance can be more widely used in genetic engineering, especially in the production of nucleic acid drugs. To improve the salt tolerance of DSN, we selected five DNA-binding domains from extremophilic organisms, which have been shown the ability to improve salt tolerance of DNA polymerases and nucleases. The experimental results demonstrated that the fusion protein TK-DSN produced by fusing a N-terminal DNA-binding domain, which comprised two HhH (helix–hairpin–helix) motifs domain from an extremely halotolerant bacterium Thioalkalivibrio sp. K90mix, has a significantly improved salt tolerance. TK-DSN can tolerate the concentration of NaCl up to 800 mM; in addition, the ability of digesting DNA was also enhanced during in vitro transcription and RNA purification. This strategy provides the method for the personalized customization of biological tool enzymes for different applications.