Uncoupling of Nucleotide Hydrolysis and Polymerization in the ParA Protein Superfamily Disrupts DNA Segregation Dynamics

• Published in: The Journal of biological chemistry 2012-12, Vol.287 (51), p.42545-42553
• Main Authors: Dobruk-Serkowska, Aneta, Caccamo, Marisa, Rodríguez-Castañeda, Fernando, Wu, Meiyi, Bryce, Kerstyn, Ng, Irene, Schumacher, Maria A., Barillà, Daniela, Hayes, Finbarr
• Format: Article
• Language: English
• Subjects: 1-Acylglycerol-3-Phosphate O-Acyltransferase - chemistry; 1-Acylglycerol-3-Phosphate O-Acyltransferase - metabolism; Adenosine Triphosphatases - metabolism; Adenosine Triphosphate - metabolism; Amino Acid Motifs; Amino Acid Sequence; Arginine - metabolism; ATPases; Bacteria; Binding Sites; Chromosome Segregation; Conserved Sequence; Crystallography, X-Ray; DNA, Bacterial - metabolism; Escherichia coli; Escherichia coli - metabolism; Escherichia coli Proteins - chemistry; Escherichia coli Proteins - metabolism; Fluorescence Polarization; Hydrolysis; Kinetics; Microbiology; Molecular Biology; Molecular Sequence Data; Multigene Family; Mutant Proteins - chemistry; Mutant Proteins - metabolism; Mutation - genetics; Nucleotides - metabolism; ParA; ParF; Partition; Plasmid; Polymerization; Protein Binding; Protein Self-assembly; Protein Structure and Folding
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.410324

DNA segregation in bacteria is mediated most frequently by proteins of the ParA superfamily that transport DNA molecules attached via the segrosome nucleoprotein complex. Segregation is governed by a cycle of ATP-induced polymerization and subsequent depolymerization of the ParA factor. Here, we establish that hyperactive ATPase variants of the ParA homolog ParF display altered segrosome dynamics that block accurate DNA segregation. An arginine finger-like motif in the ParG centromere-binding factor augments ParF ATPase activity but is ineffective in stimulating nucleotide hydrolysis by the hyperactive proteins. Moreover, whereas polymerization of wild-type ParF is accelerated by ATP and inhibited by ADP, filamentation of the mutated proteins is blocked indiscriminately by nucleotides. The mutations affect a triplet of conserved residues that are situated neither in canonical nucleotide binding and hydrolysis motifs in the ParF tertiary structure nor at interfaces implicated in ParF polymerization. Instead the residues are involved in shaping the contours of the binding pocket so that nucleotide binding locks the mutant proteins into a configuration that is refractory to polymerization. Thus, the architecture of the pocket not only is crucial for optimal ATPase kinetics but also plays a key role in the polymerization dynamics of ParA proteins that drive DNA segregation ubiquitously in procaryotes. Background: The ParA superfamily of polymerizing ATPases mediates DNA segregation ubiquitously in bacteria. Results: Hyperactive ATPase variants of the ParA homolog, ParF, are defective in polymerization and segregation. Conclusion: Conserved residues situated neither in canonical ATP motifs nor at interfaces implicated in ParF polymerization are crucial for protein function. Significance: The architecture of the ParA nucleotide-binding pocket is key to precise DNA segregation.