Probably involved in the repair of mismatches in DNA. Component of the DNA mismatch repair (MMR) complex composed at least of MSH2, MSH3, MSH6, PMS1 and MLH1 (PubMed:26300262). The MutL-beta complex is a heterodimer of PMS1 and MLH1 (PubMed:10748105). Interacts with MCM9 (PubMed:26300262). Belongs to the DNA mismatch repair MutL/HexB family.