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Chimeric Saccharomyces cerevisiae Msh6 protein with an Msh3 mispair-binding domain combines properties of both proteins

Shell, Scarlet S., Putnam, Christopher D., Kolodner, Richard D.
Proceedings of the National Academy of Sciences of the United States of America 2007 v.104 no.26 pp. 10956-10961
Saccharomyces cerevisiae, yeasts, recombinant proteins, DNA-binding proteins, DNA repair, binding sites, nucleotide sequences, DNA replication
Msh2-Msh3 and Msh2-Msh6 are two partially redundant mispair-recognition complexes that initiate mismatch repair in eukaryotes. Crystal structures of the prokaryotic homolog MutS suggest the mechanism by which Msh6 interacts with mispairs because key mispair-contacting residues are conserved in these two proteins. Because Msh3 lacks these conserved residues, we constructed a series of mutants to investigate the requirements for mispair interaction by Msh3. We found that a chimeric protein in which the mispair-binding domain (MBD) of Msh6 was replaced by the equivalent domain of Msh3 was functional for mismatch repair. This chimera possessed the mispair-binding specificity of Msh3 and revealed that communication between the MBD and the ATPase domain is conserved between Msh2-Msh3 and Msh2-Msh6. Further, the chimeric protein retained Msh6-like properties with respect to genetic interactions with the MutL homologs and an Msh2 MBD deletion mutant, indicating that Msh3-like behaviors beyond mispair specificity are not features controlled by the MBD.