The Escherichia coli MutL protein physically interacts with MutH and stimulates the MutH-associated endonuclease activity.
All possible pairwise combinations of UvrD, MutL, MutS, and MutH were tested using the yeast two-hybrid system to identify potential interactions involving mismatch repair proteins. A two-hybrid screen previously identified a physical interaction between MutL and UvrD. Although several other known interactions were not observed, a novel interaction between MutL and MutH was detected. A series of truncations from the NH2 and COOH termini of MutL demonstrated that the COOH-terminal 218 amino acids were sufficient for the two-hybrid interaction with MutH. Removal of a small number of residues from either the NH2 or COOH termini of MutH eliminated the two-hybrid interaction with MutL. Protein affinity chromatography experiments confirmed that MutL, but not MutS, physically associates with MutH. Furthermore, MutL greatly stimulated the d(GATC)-specific endonuclease activity of MutH in the absence of MutS and a mispaired base. Stimulation of the MutH-associated endonuclease activity by MutL was dependent on ATP binding but not ATP hydrolysis. Further stimulation of this reaction by MutS required the presence of a DNA mismatch and a hydrolyzable form of ATP. These results suggest that MutL activates the MutH-associated endonuclease activity through a physical interaction during methyl-directed mismatch repair in Escherichia coli.
Hall
M C
MC
Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Matson
S W
SW
D000251:Adenosine Triphosphatases; D000255:Adenosine Triphosphate / Q000378:metabolism; D000266:Adenylyl Imidodiphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D020137:Base Pair Mismatch; D002846:Chromatography, Affinity; D004260:DNA Repair; D045643:DNA Repair Enzymes; D004269:DNA, Bacterial / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004706:Endodeoxyribonucleases / Q000378:metabolism*; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D006868:Hydrolysis; D000070956:MutL Proteins
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C074770:MutL protein, E coli; D000266:Adenylyl Imidodiphosphate; D000255:Adenosine Triphosphate; D004706:Endodeoxyribonucleases; C059682:methyl-directed mismatch repair protein, E coli; D000251:Adenosine Triphosphatases; D000070956:MutL Proteins; D045643:DNA Repair Enzymes