Abstract: A method and a kit for detecting a mutation from a non-mutated sequence of a target polynucleotide in a sample, by using a mismatch binding protein. The method comprises: a) providing non-mutated and mutated target polynucleotide; b) forming duplex of the non-mutated and mutated single strands of the target polynucleotide in a); c) adding a single strand binding protein to the polynucleotide from b); d) incubating the mismatch binding protein with an activating agent; e) adding the incubated mismatch binding protein from d) to the polynucleotide from c), whereby the mismatch binding protein binds to the duplex formed by one non-mutated and one mutated single strand of the target polynucleotide; f) detecting the presence of any mismatch binding protein bound to the target polynucleotide.