Dual recognition-incision enzymes might be involved in mismatch repair andmeiosis

Mismatch repair in many organisms depends on three proteins: the mismatch-r ecognition protein MutS, a nicking endonuclease MutH, and MutL, which acts as a scaffold between these. However, many genomes lack MutL but possess Mu tS. In one of these cases, in a coral mitochondrial genome, a gene is prese nt that encodes a MutS protein fused to an HNH nicking endonuclease, potent ially eliminating the requirement for MutL, Likewise, many prokaryotes coul d operate similarly, independently of MutL by encoding a fused MutS-Smr (Mu tS2) protein. Smr, which is proposed to be a nicking endonuclease, can also be found separately in many eukaryotes, where it might play a role in mism atch repair or meiotic chromosome crossing-over.