Very short patch repair

Very short patch (VSP) repair is a DNA repair system that removes GT mismatches created by the deamination of 5-methylcytosine to thymine. This system exists because the glycosylases which normally target deaminated bases cannot target thymine (it being one of the regular four bases in DNA). Very short patch (VSP) repair is a DNA repair system that removes GT mismatches created by the deamination of 5-methylcytosine to thymine. This system exists because the glycosylases which normally target deaminated bases cannot target thymine (it being one of the regular four bases in DNA). The components of the system are MutS, which binds to the GT mismatch, the VSR endonuclease, which cuts the DNA, and MutL, which recruits the UvrD helicase. VSR (very short patch repair) endonucleases occur in a variety of bacteria. They work by cutting, or rather, making a nick in DNA if the base pair is mutated or damaged.