title: Dimerization of Escherichia coli UvrA and its binding to undamaged and ultraviolet light damaged DNA.
abstract: The initial stages in the repair of damaged DNA by the Escherichia coli uvr system involve the recognition of damage by UvrA. We have examined in detail the binding of UvrA to DNA randomly damaged by ultraviolet light, undamaged DNA, and single-stranded DNA using nitrocellulose filter binding and gel mobility shift assays to arrive at the following model: UvrA dimers bind specifically to damaged DNA both in the presence and in the absence of ATP. The dimerization of UvrA is promoted by UvrA concentrations greater than 1 nM, the presence of ATP, or physiological temperatures, and the dimerization step dominates the temperature dependence of UvrA binding to DNA damaged by ultraviolet light. The apparent association constant for specific binding is dependent on the concentration of UvrA due to coupled dimerization, aggregation, and nonspecific binding reactions. At 1 nM UvrA, either with or without ATP, Kuv approximately 10(9) M-1. The binding of UvrA to undamaged DNA is 10(3)-10(4)-fold weaker than the damage-specific binding. Both the strength of damage-specific binding and the discrimination between damaged and undamaged sites are affected by the salt concentration. The kinetics of association and dissociation reactions indicate that the primary effects of ATP are on the extent of UvrA dimerization rather than on the properties of the UvrA-uvDNA complex. The complexity of the interaction of UvrA, ATP, and DNA is indicated by the opposing effects of ATP binding and hydrolysis on UvrA dimerization.
authors.affiliation: Department of Biochemistry, Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland 21205.
authors.forename: S J
authors.initials: SJ
authors.lastname: Mazur
authors.forename: L
authors.initials: L
authors.lastname: Grossman
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics* / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001667:Binding, Competitive; D003101:Collodion; D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication; D004269:DNA, Bacterial / Q000378:metabolism / Q000528:radiation effects*; D004277:DNA, Single-Stranded / Q000378:metabolism / Q000528:radiation effects; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000528:radiation effects; D029968:Escherichia coli Proteins; D007700:Kinetics; D008851:Micropore Filters; D013816:Thermodynamics; D014466:Ultraviolet Rays
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D000255:Adenosine Triphosphate; D003101:Collodion; C068631:UvrA protein, E coli; D000251:Adenosine Triphosphatases