MutS-1

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MutS is a DNA mismatch repair protein first described in Escherichia coli. It helps keep DNA accurate by fixing errors that slip past the DNA polymerase proofreading step during replication. After replication, MutS teams up with other proteins (MutL and MutH) to remove the wrong piece of DNA so the correct sequence can be rebuilt.

MutS forms a dimer, with one subunit mainly recognizing the mismatch while both subunits grip the DNA to form a clamp. When MutS binds a mismatch, it triggers binding of ATP and a shape change that turns MutS into a sliding clamp that moves along DNA to recruit the rest of the repair machinery. MutS is part of a large MutS family found across bacteria, archaea, and eukaryotes, with many related proteins that can have different functions.

The N-terminal part of MutS is responsible for recognizing mismatches and has a special fold that helps it bind DNA. Binding to a mismatch can bend the DNA, which helps start the repair process. Certain MutS-related interactions (involving key amino acids) help stabilize different types of mismatches.

MutS also collaborates with other enzymes to repair certain chemical damages to DNA, such as O6-methylguanine, which could otherwise mispair during replication. In humans, MutS-like proteins (MSH1–MSH6) are important for preventing cancer when they function properly.