MutS is a mismatch repair enzyme from Escherichia coli, expressed in the recombinant form in the same host, which selectively binds DNA fragments containing mispaired or unpaired bases. MutS binds mismatches that most resemble base pairs (i.e., G:T mismatches in G:C rich regions), allowing MutS to be used for mutation/SNP detection, isolation applications and mismatch repair structure/function studies.