Biophysical science Institute

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Biophysical science Institute

science, United Kingdom

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Quinlan R.A.,Biophysical science Institute | Zhang Y.,CAS Institute of Biophysics | Lansbury A.,Biophysical science Institute | Williamson I.,Durham University | And 3 more authors.
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2013

The archael small heat-shock protein (sHSP), MjHSP16.5, forms a 24-subunit oligomer with octahedral symmetry. Here, we demonstrate that the IXI motif present in the C-terminal domain is necessary for the oligomerization of MjHSP16.5. Removal increased the in vitro chaperone activity with citrate synthase as the client protein. Less predictable were the effects of the R107G substitution in MjHSP16.5 because of the differences in the oligomerization of metazoan and non-metazoan sHSPs. We present the crystal structure for MjHSP16.5 R107G and compare this with an improved (2.5 A °) crystal structure for wild-type (WT) MjHSP16.5. Although no significant structural differences were found in the crystal, using cryo-electron microscopy, we identified two 24mer species with octahedral symmetry for the WT MjHSP16.5 both at room temperature and at 608C, all showing two major species with the same diameter of 12.4 nm. Similarly, at room temperature, there are also two kinds of 12.4 nm oligomers for R107G MjHSP16.5, but in the 608C sample, a larger 24mer species with a diameter of 13.6 nm was observed with significant changes in the fourfold symmetry axis and dimer-dimer interface. This highly conserved arginine, therefore, contributes to the quaternary organization of non-metazoan sHSP oligomers. Potentially, the R107G substitution has functional consequences as R107G MjHSP16.5 was far superior to the WT protein in protecting bL-crystallin against heat-induced aggregation. © 2013 The Authors.


Townsend P.D.,Biophysical science Institute | Rodgers T.L.,Durham University | Glover L.C.,Biophysical science Institute | Korhonen H.J.,Biophysical science Institute | And 10 more authors.
Journal of Biological Chemistry | Year: 2015

Background: Protein allostery can be communicated purely through altered entropy. Results: Altered cAMP binding strength in CAP results in changes to entropy-driven allostery. Conclusion: The requirement to maintain allostery constrains evolution of the ligand-binding site in CAP. Significance: Entropy-driven processes can constrain amino acid covariation in evolution. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.


PubMed | Wageningen University, University of Amsterdam, Durham University and Biophysical science Institute
Type: Journal Article | Journal: The Journal of biological chemistry | Year: 2015

Plant nucleotide-binding leucine-rich repeat (NLR) proteins enable cells to respond to pathogen attack. Several NLRs act in the nucleus; however, conserved nuclear targets that support their role in immunity are unknown. Previously, we noted a structural homology between the nucleotide-binding domain of NLRs and DNA replication origin-binding Cdc6/Orc1 proteins. Here we show that the NB-ARC (nucleotide-binding, Apaf-1, R-proteins, and CED-4) domain of the Rx1 NLR of potato binds nucleic acids. Rx1 induces ATP-dependent bending and melting of DNA in vitro, dependent upon a functional P-loop. In situ full-length Rx1 binds nuclear DNA following activation by its cognate pathogen-derived effector protein, the coat protein of potato virus X. In line with its obligatory nucleocytoplasmic distribution, DNA binding was only observed when Rx1 was allowed to freely translocate between both compartments and was activated in the cytoplasm. Immune activation induced by an unrelated NLR-effector pair did not trigger an Rx1-DNA interaction. DNA binding is therefore not merely a consequence of immune activation. These data establish a role for DNA distortion in Rx1 immune signaling and define DNA as a molecular target of an activated NLR.

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