title: Ca2+ activates human homologous recombination protein Rad51 by modulating its ATPase activity.
abstract: Human Rad51 (hRad51) protein plays a key role in homologous recombination and DNA repair. hRad51 protein forms a helical filament on single-stranded DNA (ssDNA), which performs the basic steps of homologous recombination: a search for homologous double-stranded DNA (dsDNA) and DNA strand exchange. hRad51 protein possesses DNA-dependent ATPase activity; however, the role of this activity has not been understood. Our current results show that Ca(2+) greatly stimulates DNA strand exchange activity of hRad51 protein. We found that Ca(2+) exerts its stimulatory effect by modulating the ATPase activity of hRad51 protein. Our data demonstrate that, in the presence of Mg(2+), the hRad51-ATP-ssDNA filament is quickly converted to an inactive hRad51-ADP-ssDNA form, due to relatively rapid ATP hydrolysis and slow dissociation of ADP. Ca(2+) maintains the active hRad51-ATP-ssDNA filament by reducing the ATP hydrolysis rate. These findings demonstrate a crucial role of the ATPase activity in regulation of DNA strand exchange activity of hRad51 protein. This mechanism of Rad51 protein regulation by modulating its ATPase activity is evolutionarily recent; we found no such mechanism for yeast Rad51 (yRad51) protein.
authors.affiliation: Department of Biochemistry, Drexel University College of Medicine, Philadelphia, PA 19102-1192, USA.
authors.forename: Dmitry V
authors.initials: DV
authors.lastname: Bugreev
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Mazin
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology*; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D051135:Rad51 Recombinase; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D004268:DNA-Binding Proteins; D012965:Sodium Chloride; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D004247:DNA; D051135:Rad51 Recombinase; D000251:Adenosine Triphosphatases; D008274:Magnesium; D002118:Calcium