[High expression and identification of DNA mismatch repair gene mutS in Escherichia coli]

DNA mismatch repair gene mutS (2.56 kb) was PCR modified and cloned into a secretive prokaryotic expression vector pET32a (+) which carries a N-terminal His.tag + and thioredoxin sequence. MutS protein was expressed with high level after IPTG induction using the strain E. coli AD494(DE3). SDS-PAGE revealed that the expected protein with a molecular weight of 108 kD which is about 35% of the total bacterial proteins is almost soluble. The expected protein was purified directly by immobilized metal (Ni2+) chelation affinity chromatography and the purity is over 90%. MutS protein activity verified using mismatch DNA showed that the expression product can recognize and bind to base-pair mismatch specifically.