title: Differential and simultaneous adenosine di- and triphosphate binding by MutS.
abstract: The roles of ATP binding and hydrolysis in the function of MutS in mismatch repair are poorly understood. As one means of addressing this question, we have determined the affinities and number of adenosine di- and triphosphate binding sites within MutS. Nitrocellulose filter binding assay and equilibrium fluorescence anisotropy measurements have demonstrated that MutS has one high affinity binding site for ADP and one high affinity site for nonhydrolyzable ATP analogues per dimer equivalent. Low concentrations of 5'-adenylylimidodiphosphate (AMPPNP) promote ADP binding and a large excess of AMPPNP is required to displace ADP from the protein. Fluorescence energy transfer and filter binding assays indicate that ADP and nonhydrolyzable ATP analogues can bind simultaneously to adjacent subunits within the MutS oligomer with affinities in the low micromolar range. These findings suggest that the protein exists primarily as the ATP.MutS.ADP ternary complex in solution and that this may be the form of the protein that is involved in DNA encounters in vivo.
authors.affiliation: Department of Biochemistry and Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: Keith P
authors.initials: KP
authors.lastname: Bjornson
authors.forename: Paul
authors.initials: P
authors.lastname: Modrich
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism* / Q000494:pharmacology; D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000266:Adenylyl Imidodiphosphate / Q000737:chemistry / Q000378:metabolism; D016880:Anisotropy; D001426:Bacterial Proteins; D020137:Base Pair Mismatch; D001665:Binding Sites; D001667:Binding, Competitive; D001896:Boron Compounds / Q000494:pharmacology; D004260:DNA Repair; D004268:DNA-Binding Proteins; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes / Q000494:pharmacology; D006868:Hydrolysis; D051719:MutS DNA Mismatch-Binding Protein; D011485:Protein Binding
chemical_list: C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D001426:Bacterial Proteins; D001896:Boron Compounds; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D005456:Fluorescent Dyes; D000266:Adenylyl Imidodiphosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D051719:MutS DNA Mismatch-Binding Protein; C497175:MutS protein, E coli