Partitioning of plasmid R1. The ParM protein exhibits ATPase activity and interacts with the centromere-like ParR-parC complex.
The parA system of plasmid R1 consists of two genes, parM and parR, and a cis-acting centromere-like site parC. The ParM protein exhibits similarity with a superfamily of ATPases that includes actin, hsp70 and hexokinase. ParM was purified to near-homogeneity and assayed for in vitro ATPase activity. The wild-type ParM protein was found to posses ATPase activity. Mutant ParM derivatives that exhibited decreased in vitro ATPase activity were non-functional in vivo, indicating that the ATP turnover by ParM is essential for correct plasmid partitioning. The mutant ParM proteins exhibited trans-dominance, suggesting that ParM participates as a structural component of the partitioning apparatus. The ATPase activity of ParM was activated slightly by the presence of ParR and activated to a much greater extent when ParR was bound to the centromere-like parC region. An analysis using the yeast two-hybrid system indicated that ParM and ParR interact, and demonstrated that ParR interacts with itself. Thus our results suggest a direct interaction of ParM and ParR at the natural partition site parC, and that the ATPase activity of ParM is specifically stimulated by this interaction.
Jensen
R B
RB
Department of Molecular Biology, Odense University, Denmark.
Gerdes
K
K
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002503:Centromere; D027101:DNA Topoisomerase IV; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D009154:Mutation; D011815:R Factors / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*
D001426:Bacterial Proteins; C086169:ParR protein, bacteria; D012097:Repressor Proteins; C052883:chromosome partition proteins, bacterial; D000251:Adenosine Triphosphatases; D027101:DNA Topoisomerase IV; D004250:DNA Topoisomerases, Type II