MutS and MutL activate DNA helicase II in a mismatch-dependent manner.
MutS, MutL, and DNA helicase II are required for the mismatch-provoked excision step that occurs during Escherichia coli methyl-directed mismatch repair. In this study MutL is shown to enhance the unwinding activity of DNA helicase II more than 10-fold on a conventional helicase substrate in which a 35-residue oligonucleotide is annealed to a M13 circular single-stranded phage DNA under conditions where the two proteins are present at approximately molar stoichiometry with respect to the substrate. MutS- and MutL-dependent activation of DNA helicase II has also been demonstrated with a model substrate in which a 138-residue oligonucleotide was hybridized to a 138-nucleotide gap in an otherwise duplex 7,100-base pair circular DNA. Displacement of the oligonucleotide requires MutS, MutL, DNA helicase II, and ATP and is dependent on the presence of a mismatch within the hybrid region. Although DNA helicase II and Rep helicase share substantial sequence homology and features of mechanism, Rep helicase is inactive in this reaction.
Yamaguchi
M
M
Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA.
Dao
V
V
Modrich
P
P
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D004265:DNA Helicases; D004260:DNA Repair; D004270:DNA, Circular / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins; D004789:Enzyme Activation; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D007700:Kinetics; D000070956:MutL Proteins; D051719:MutS DNA Mismatch-Binding Protein; D009692:Nucleic Acid Heteroduplexes / Q000378:metabolism; D009838:Oligodeoxyribonucleotides; D013379:Substrate Specificity
D001426:Bacterial Proteins; D004270:DNA, Circular; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C074770:MutL protein, E coli; D009692:Nucleic Acid Heteroduplexes; D009838:Oligodeoxyribonucleotides; C506744:rep protein, E coli; D000251:Adenosine Triphosphatases; D000070956:MutL Proteins; D051719:MutS DNA Mismatch-Binding Protein; C497175:MutS protein, E coli; D004265:DNA Helicases