2Q2K: Structure Of Nucleic-Acid Binding Protein

The stable inheritance of genetic material depends on accurate DNA partition. Plasmids serve as tractable model systems to study DNA segregation because they require only a DNA centromere, a centromere-binding protein and a force-generating ATPase. The centromeres of partition (par) systems typically consist of a tandem arrangement of direct repeats. The best-characterized par system contains a centromere-binding protein called ParR and an ATPase called ParM. In the first step of segregation, multiple ParR proteins interact with the centromere repeats to form a large nucleoprotein complex of unknown structure called the segrosome, which binds ParM filaments. pSK41 ParR binds a centromere consisting of multiple 20-base-pair (bp) tandem repeats to mediate both transcription autoregulation and segregation. Here we report the structure of the pSK41 segrosome revealed in the crystal structure of a ParR-DNA complex. In the crystals, the 20-mer tandem repeats stack pseudo-continuously to generate the full-length centromere with the ribbon-helix-helix (RHH) fold of ParR binding successive DNA repeats as dimer-of-dimers. Remarkably, the dimer-of-dimers assemble in a continuous protein super-helical array, wrapping the DNA about its positive convex surface to form a large segrosome with an open, solenoid-shaped structure, suggesting a mechanism for ParM capture and subsequent plasmid segregation.
PDB ID: 2Q2KDownload
MMDB ID: 62232
PDB Deposition Date: 2007/5/28
Updated in MMDB: 2012/09
Experimental Method:
x-ray diffraction
Resolution: 3  Å
Source Organism:
synthetic construct
Similar Structures:
Biological Unit for 2Q2K: hexameric; determined by author
Molecular Components in 2Q2K
Label Count Molecule
Proteins (4 molecules)
Hypothetical Protein
Molecule annotation
Nucleotide(1 molecule)
DNA (5'-d(*ap*gp*tp*ap*tp*ap*(5iu)p*ap*cp*(5iu) P*ap*gp*tp*ap*tp*ap*tp*ap*cp*t)-3')
Molecule annotation
Chemicals (2 molecules)
* Click molecule labels to explore molecular sequence information.

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