Structural Mechanism of ATP-induced Polymerization of the Partition Factor ParF

Abstract

Background: ParF and ParG mediate TP228 plasmid segregation. Results: ATP binding to ParF activates segregation, and ADP binding to ParF antagonizes its segregation function. ParF-ADP is monomeric, and ParF-ATP is dimeric. ParF dimers assemble into polymers. Conclusion: ParF-ATP dimers serve as building blocks for polymer assembly. Significance: ParF-ATP polymers provide a mechanism for plasmid segregation.

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

“…Structures of monomeric ParF bound to ADP recently revealed that the protein adopts an ␣-␤-␣ layered structure with a central sevenstranded ␤-sheet surrounded by several ␣-helices. The adenine nucleotide is situated on the C-terminal side of the parallel ␤-sheets and is recognized by nucleotide-binding motifs including the Walker A box (29). By contrast with ParF-ADP, ParF forms nucleotide sandwich dimers when bound to AMP-PCP.…”

“…This patch inserts into a niche close to the adenine nucleotide-binding pocket of the adjacent subunit in ParF sandwich dimers (29). Considering its location near the Walker A motif in the ParF structure, the P104A change is expected to exert short range impacts on binding pocket conformation (Fig.…”

“…By contrast with ParF-ADP, ParF forms nucleotide sandwich dimers when bound to AMP-PCP. These sandwich dimers pack into higher order, dimer of dimer units to produce a distinctive linear filament that reflects ParF polymer assembly (29).…”

“…Centromere-binding proteins with diverse primary sequences elicit equivalent polymerization responses with their cognate ParA homologs, indicating a conserved mechanism of polymerization enhancement within the ParA superfamily (16, 20 -22). In contrast with ATP, ADP represses ParF polymerization, suggesting that subcellular plasmid movement is driven by a cycle of ParF polymer assembly and disassembly that reflects the nucleotide-bound state of the protein (15,29).…”

“…In contrast, ParF bound to the nonhydrolyzable ATP analog AMPPCP 7 forms dimers that pack into dimer of dimer building blocks that assemble into polymers (29). ParG possesses an arginine finger-like motif in its flexible N-terminal tail that stimulates ATP hydrolysis by ParF.…”