Engineered SNAP-MBD2b proteins for specific recognition of methylated DNA

摘要

Methyl-CpG-binding domain(MBD)proteins can specifically recognize and bind methylated CpG sites of DNA,thus repress gene transcription.In this study,we designed and expressed two recombinant proteins,MBD2b and SNAP-MBD2b,in E.coli.An optimized protocol was developed to purify the proteins using Ni-NTA affinity cartridge and cation exchange resin.The engineered proteins purified by this method exhibited more than 93%purity and high binding avidity.We found that both SNAP-MBD2b and MBD2b were prone to aggregate during dialysis.However,this could be prevented by the use of 0.3 mol/L NaCl.The fusion of SNAP-tag with MBD2b significantly enhanced the expression of MBD2b protein in E.coli and reduced the adsorption of MBD2b on solid interfaces involved in protein purification and immobilization.The engineered proteins can be used for the study of interaction with methylated DNA and the assays for DNA methylation.