title: Hexameric rings of Escherichia coli RuvB protein. Cooperative assembly, processivity and ATPase activity.
abstract: The Escherichia coli RuvA and RuvB proteins mediate ATP-dependent branch migration of Holliday junctions during homologous genetic recombination. RuvA is a DNA-binding protein with high affinity for Holliday junctions, to which it directs RuvB (a DNA-dependent ATPase). Electron microscopic studies have shown that RuvB forms double hexameric rings on duplex DNA. To determine whether the rings are biologically active, the conditions required for their formation and activity have been analysed. The quaternary structure of RuvB appears to be dependent upon the binding of ATP, magnesium ions, and the presence of RuvA. In the presence of Mg2+ and ATP, RuvB forms hexamers; however, in the presence of Mg2+ alone, dodecamers were observed. Both forms of the protein are stable and have been isolated by gel filtration. Performed dodecamers and, to a lesser extent, hexamers assembled in the absence of DNA lack ATPase activity. Maximal ATPase activity was observed when RuvB assembled directly on DNA in the presence of Mg2+ and ATP. Moreover, under these conditions, a direct interaction between RuvB hexamers and tetramers of RuvA was observed.
authors.affiliation: Imperial Cancer Research Fund, Clare Hall Laboratories, South Mimms, Herts, U.K.
authors.forename: A H
authors.initials: AH
authors.lastname: Mitchell
authors.forename: S C
authors.initials: SC
authors.lastname: West
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001704:Biopolymers / Q000378:metabolism; D004265:DNA Helicases; D004269:DNA, Bacterial / Q000378:metabolism; D004270:DNA, Circular / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins; D007700:Kinetics; D011487:Protein Conformation; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D001704:Biopolymers; D004269:DNA, Bacterial; D004270:DNA, Circular; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C061260:RuvB protein, Bacteria; C071059:Holliday junction DNA helicase, E coli; D000251:Adenosine Triphosphatases; D004265:DNA Helicases