title: Escherichia coli MutS tetramerization domain structure reveals that stable dimers but not tetramers are essential for DNA mismatch repair in vivo.
abstract: The Escherichia coli mispair-binding protein MutS forms dimers and tetramers in vitro, although the functional form in vivo is under debate. Here we demonstrate that the MutS tetramer is extended in solution using small angle x-ray scattering and the crystal structure of the C-terminal 34 amino acids of MutS containing the tetramer-forming domain fused to maltose-binding protein (MBP). Wild-type C-terminal MBP fusions formed tetramers and could bind MutS and MutS-MutL-DNA complexes. In contrast, D835R and R840E mutations predicted to disrupt tetrameric interactions only allowed dimerization of MBP. A chromosomal MutS truncation mutation eliminating the dimerization/tetramerization domain eliminated mismatch repair, whereas the tetramer-disrupting MutS D835R and R840E mutations only modestly affected MutS function. These results demonstrate that dimerization but not tetramerization of the MutS C terminus is essential for mismatch repair.
authors.affiliation: Ludwig Institute for Cancer Research, Department of Medicine, University of California, San Diego School of Medicine, La Jolla, California 92093-0669, USA.
authors.forename: Marc L
authors.initials: ML
authors.lastname: Mendillo
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Putnam
authors.forename: Richard D
authors.initials: RD
authors.lastname: Kolodner
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019943:Amino Acid Substitution; D002876:Chromosomes, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D004260:DNA Repair; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000070956:MutL Proteins; D051719:MutS DNA Mismatch-Binding Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D011485:Protein Binding / Q000235:genetics; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C074770:MutL protein, E coli; D000251:Adenosine Triphosphatases; D000070956:MutL Proteins; D051719:MutS DNA Mismatch-Binding Protein