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Published on: July 19, 2024
Mapping the dimer interface in the C-terminal domains of the yeast MLH1-PMS1 heterodimer
Jenny M Cutalo1, Thomas A Darden, Thomas A Kunkel
1Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, P.O. Box 12233, Research Triangle Park, North Carolina 27709, USA.
Abstract:
Yeast MutLalpha is a heterodimer of MLH1 and PMS1 that participates in a variety of DNA transactions, including DNA mismatch repair. Formation of the MutLalpha heterodimer requires that the C-terminal domains of MLH1 and PMS1 interact in a manner that is not yet fully understood. Here we investigate the interactions involved in heterodimerization. Using protein surface modification and mass spectrometry, we identify numerous lysine residues that are exposed to solvent in monomeric MLH1. A corresponding analysis of the MLH1-PMS1 heterodimer reveals that three of these exposed residues, K665, K675, and K704, are no longer solvent accessible in the heterodimer, suggesting that they are within the dimer interface. We refine secondary structure predictions and sequence alignments of C-terminal residues of seven eukaryotic MutL homologues and then develop homology models for the N- and C-terminal domains of MLH1. On the basis of this information, we present a model for interaction of the C-terminal domains of MLH1 and PMS1.
Insights
Yeast MutLalpha, a DNA mismatch repair complex, forms through interactions between MLH1 and PMS1 proteins. This study identifies specific lysine residues on MLH1 crucial for the heterodimer formation.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Yeast MutLalpha, a heterodimer of MLH1 and PMS1, is essential for DNA mismatch repair.
- The precise mechanism of MutLalpha heterodimerization via C-terminal domain interaction remains unclear.
Purpose of the Study:
- To investigate the molecular interactions driving MLH1-PMS1 heterodimer formation.
- To identify key residues involved in the C-terminal domain interaction of MutLalpha.
Main Methods:
- Protein surface modification and mass spectrometry were employed to analyze solvent-exposed lysine residues.
- Secondary structure predictions, sequence alignments, and homology modeling were used to develop interaction models.
Main Results:
- Numerous solvent-exposed lysine residues were identified in monomeric MLH1.
- Three specific lysine residues (K665, K675, K704) in MLH1 were found to be buried within the MLH1-PMS1 heterodimer interface.
- A model for the interaction of MLH1 and PMS1 C-terminal domains was proposed.
Conclusions:
- The study elucidates critical lysine residues mediating MLH1-PMS1 heterodimerization.
- The findings provide a structural basis for understanding MutLalpha complex formation and its role in DNA repair.
