Both ATPase sites of Escherichia coli UvrA have functional roles in nucleotide excision repair.
The roles of the two tandemly arranged putative ATP binding sites of Escherichia coli UvrA in UvrABC endonuclease-mediated excision repair were analyzed by site-directed mutagenesis and biochemical characterization of the representative mutant proteins. Evidence is presented that UvrA has two functional ATPase sites which coincide with the putative ATP binding motifs predicted from its amino acid sequence. The individual ATPase sites can independently hydrolyze ATP. The C-terminal ATPase site has a higher affinity for ATP than the N-terminal site. The invariable lysine residues at the ends of the glycine-rich loops of the consensus Walker type "A" motifs are indispensable for ATP hydrolysis. However, the mutations at these lysine residues do not significantly affect ATP binding. UvrA, with bound ATP, forms the most favored conformation for DNA binding. The initial binding of UvrA to DNA is chiefly at the undamaged sites. In contrast to the wild type UvrA, the ATPase site mutants bind equally to damaged and undamaged sites. Dissociation of tightly bound nucleoprotein complexes from the undamaged sites requires hydrolysis of ATP by the C-terminal ATPase site of UvrA. Thus, both ATP binding and hydrolysis are required for the damage recognition step enabling UvrA to discriminate between damaged and undamaged sites on DNA.
Thiagalingam
S
S
Department of Biochemistry, Johns Hopkins University, School of Hygiene and Public Health, Baltimore, Maryland 21205.
Grossman
L
L
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D004249:DNA Damage; D004260:DNA Repair; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004307:Dose-Response Relationship, Radiation; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D029968:Escherichia coli Proteins; D008961:Models, Structural; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015345:Oligonucleotide Probes; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D014466:Ultraviolet Rays
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D015345:Oligonucleotide Probes; D011994:Recombinant Proteins; D000255:Adenosine Triphosphate; C068631:UvrA protein, E coli; D000251:Adenosine Triphosphatases