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Biochem J. 2017 Aug 30;474(18):3121-3135. doi: 10.1042/BCJ20170281.

Intrinsic disorder in the partitioning protein KorB persists after co-operative complex formation with operator DNA and KorA.

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School of Biosciences, University of Birmingham, Birmingham B15 2TT, U.K.
Institut Laue Langevin, 71 avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France.
School of Biosciences, University of Birmingham, Birmingham B15 2TT, U.K.
Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, U.K.
School of Biosciences, University of Nottingham, Sutton Bonington Campus, Leicestershire LE12 5RD, U.K.
ISIS Neutron and Muon Spallation Source and Research Complex at Harwell, Rutherford Appleton Laboratory, Oxfordshire, U.K.


The ParB protein, KorB, from the RK2 plasmid is required for DNA partitioning and transcriptional repression. It acts co-operatively with other proteins, including the repressor KorA. Like many multifunctional proteins, KorB contains regions of intrinsically disordered structure, existing in a large ensemble of interconverting conformations. Using NMR spectroscopy, circular dichroism and small-angle neutron scattering, we studied KorB selectively within its binary complexes with KorA and DNA, and within the ternary KorA/KorB/DNA complex. The bound KorB protein remains disordered with a mobile C-terminal domain and no changes in the secondary structure, but increases in the radius of gyration on complex formation. Comparison of wild-type KorB with an N-terminal deletion mutant allows a model of the ensemble average distances between the domains when bound to DNA. We propose that the positive co-operativity between KorB, KorA and DNA results from conformational restriction of KorB on binding each partner, while maintaining disorder.


circular dichroism; intrinsically disordered proteins; protein–DNA interactions; protein–protein interactions; small-angle scattering; transcription regulation

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