Order and disorder in the domain organization of the plasmid partition protein KorB

J Biol Chem. 2010 May 14;285(20):15440-15449. doi: 10.1074/jbc.M109.096099. Epub 2010 Mar 3.

Abstract

The plasmid partition protein KorB has a dual role: it is essential for the correct segregation of the low copy number broad host range RK2 plasmid while also being an important regulator of transcription. KorB belongs to the ParB family of proteins, and partitioning in RK2 has been studied as a simplified model of bacterial chromosome segregation. Structural information on full-length ParB proteins is limited, mainly due to the inability to grow crystals suitable for diffraction studies. We show, using CD and NMR, that KorB has regions of significant intrinsic disorder and hence it adopts a multiplicity of conformations in solution. The biophysical data are consistent with bioinformatic predictions based on the amino acid sequence that the N-terminal region and also the region between the central DNA-binding domain and the C-terminal dimerization domain are intrinsically disordered. We have used small angle x-ray scattering data to determine the ensemble of solution conformations for KorB and selected deletion mutants, based on models of the known domain structures. This conformational range of KorB is likely to be biologically required for DNA partitioning and for binding to a diverse set of partner proteins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / chemistry*
  • Circular Dichroism
  • Molecular Sequence Data
  • Nuclear Magnetic Resonance, Biomolecular
  • Plasmids*
  • Protein Conformation
  • Sequence Homology, Amino Acid

Substances

  • Bacterial Proteins
  • KorB protein, Plasmid RK2