title: Hydrolysis of ATP dependent on homologous double-stranded DNA and single-stranded fragments promoted by RecA protein of Escherichia coli.
abstract: RecA protein is essential to general genetic recombination in Escherichia coli. In the presence of ATP, a stoichiometric amount of recA protein forms D-loops from superhelical closed-circular DNA (form I DNA) and homologous single-stranded fragments, and subsequently dissociates the D-loops. Under appropriate conditions, the hydrolysis of ATP by recA protein depends on the presence of both double-stranded DNA and homologous single-stranded fragments (homology-dependent hydrolysis). In the presence of form I DNA, most of the homology-dependent hydrolysis of ATP by recA protein is related to the dissociation of D-loops rather than the formation of D-loops. RecA protein also promoted the homology-dependent hydrolysis of ATP in the presence of nicked-circular DNA (form II DNA), but unlike the case of form I DNA, this hydrolysis was associated with an increase in the amount of mature D-loops that were detected by the D-loop assay. When double-stranded DNA was superhelical, the homology-dependent hydrolysis of ATP continued at the same rate even after all the D-loops were dissociated. This correlates with our earlier observation that in the process of formation and dissociation of D-loops, form I DNA was converted to an inactive substrate without any apparent damage to the DNA, probably by the formation of a complex with recA protein. All of the observations described above can be explained by a model in which a common mechanism causes dissociation of D-loops from form I DNA, inactivation of form I DNA, and growth of D-loops in form II DNA. The mechanism might involve cooperative binding of recA protein to the duplex DNA from the site of the nascent D-loop, resulting in unidirectional unwinding of the duplex DNA.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D001426:Bacterial Proteins / Q000494:pharmacology*; D055598:Chemical Phenomena; D002621:Chemistry; D004247:DNA / Q000378:metabolism*; D004278:DNA, Superhelical / Q000378:metabolism; D004926:Escherichia coli; D006868:Hydrolysis; D011938:Rec A Recombinases
chemical_list: D001426:Bacterial Proteins; D004278:DNA, Superhelical; D000255:Adenosine Triphosphate; D004247:DNA; D011938:Rec A Recombinases