Order and Disorder in the Domain Organization of the Plasmid Partition Protein KorB

School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Journal of Biological Chemistry (Impact Factor: 4.57). 03/2010; 285(20):15440-9. DOI: 10.1074/jbc.M109.096099
Source: PubMed


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.

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