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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. Source


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. Source

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