title: The function of Asp70, Glu77 and Lys79 in the Escherichia coli MutH protein.
abstract: The MutH protein, which is part of the Dam-directed mismatch repair system of Escherichia coli, introduces nicks in the unmethylated strand of a hemi-methylated DNA duplex. The latent endonuclease activity of MutH is activated by interaction with MutL, another member of the repair system. The crystal structure of MutH suggested that the active site residues include Asp70, Glu77 and Lys79, which are located at the bottom of a cleft where DNA binding probably occurs. We mutated these residues to alanines and found that the mutant proteins were unable to complement a chromosomal mutH deletion. The purified mutant proteins were able to bind to DNA with a hemi-methylated GATC sequence but had no detectable endonuclease activity with or without MutL. Although the data are consistent with the prediction of a catalytic role for Asp70, Glu77 and Lys79, it cannot be excluded that they are also involved in binding to MutL.
authors.affiliation: Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 55 Lake Avenue, Worcester, MA 01655, USA.
authors.forename: Te-hui
authors.initials: TH
authors.lastname: Wu
authors.forename: Tamalette
authors.initials: T
authors.lastname: Loh
authors.forename: M G
authors.initials: MG
authors.lastname: Marinus
mesh_terms: D000251:Adenosine Triphosphatases; D019943:Amino Acid Substitution / Q000235:genetics*; D001224:Aspartic Acid / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D002384:Catalysis; D004247:DNA / Q000235:genetics / Q000378:metabolism; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D004706:Endodeoxyribonucleases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005816:Genetic Complementation Test; D018698:Glutamic Acid / Q000235:genetics / Q000378:metabolism*; D008239:Lysine / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D000070956:MutL Proteins; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C074770:MutL protein, E coli; D011993:Recombinant Fusion Proteins; D001224:Aspartic Acid; D018698:Glutamic Acid; D004247:DNA; D004706:Endodeoxyribonucleases; C059682:methyl-directed mismatch repair protein, E coli; D000251:Adenosine Triphosphatases; D000070956:MutL Proteins; D045643:DNA Repair Enzymes; D008239:Lysine