What role does the MutL protein play in DNA repair? (5 POINTS) It performs a proofreading function, similar to DNA polymerase, and removes incorrect bases from the template DNA strand. It recognizes and binds to a pair of "mismatched" nucleotides, preventing their translation. It recognizes the newly-synthesized DNA strand (e.g., by detecting nicks), ensuring only it—and not the template strand—is repaired. It helps to link together regions of DNA, after an error has been removed via exonuclease.

Mut L protein is involved in mismatch DNA repair. MutL protein is complexed with MutS protein and the MutL-MutS complex recognizes all the mismatched base pairs present in the newly formed DNA strand. The complex can not recognize the "C-C" pairs. MutH protein joins the complex.

The MutH protein also has a site-specific endonuclease activity and cleaves the unmethylated DNA strand towards the 5' end of the guanine base in the GATC sequence to mark the strand for DNA repair. In this way, MutL protein, along with MutS and MutH proteins mark the mismatched DNA bases for repair so that they are not translated into a faulty protein.