Browsing by Author "Devlin, GL"

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    Native disulphide-linked dimers facilitate amyloid fibril formation by bovine milk αS2-casein
    (Elsevier, 2021-03) Thorn, DC; Bahraminejad, E; Grosas, AB; Kouldelka, T; Hoffmann, P; Mata, JP; Devlin, GL; Sunde, M; Ecroyd, H; Holt, C; Carver, JA
    Bovine milk αS2-casein, an intrinsically disordered protein, readily forms amyloid fibrils in vitro and is implicated in the formation of amyloid fibril deposits in mammary tissue. Its two cysteine residues participate in the formation of either intra- or intermolecular disulphide bonds, generating monomer and dimer species. X-ray solution scattering measurements indicated that both forms of the protein adopt large, spherical oligomers at 20 °C. Upon incubation at 37 °C, the disulphide-linked dimer showed a significantly greater propensity to form amyloid fibrils than its monomeric counterpart. Thioflavin T fluorescence, circular dichroism and infrared spectra were consistent with one or both of the dimer isomers (in a parallel or antiparallel arrangement) being predisposed toward an ordered, amyloid-like structure. Limited proteolysis experiments indicated that the region from Ala81 to Lys113 is incorporated into the fibril core, implying that this region, which is predicted by several algorithms to be amyloidogenic, initiates fibril formation of αS2-casein. The partial conservation of the cysteine motif and the frequent occurrence of disulphide-linked dimers in mammalian milks despite the associated risk of mammary amyloidosis, suggest that the dimeric conformation of αS2-casein is a functional, yet amyloidogenic, structure. © 2020 Elsevier B.V
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    Quaternary organization and dynamics of the molecular chaperone HSP26 are thermally regulated
    (Elsevier, 2010-09-24) Benesch, JLP; Aquilina, JA; Baldwin, AJ; Rekas, A; Stengel, F; Lindner, RA; Basha, E; Devlin, GL; Horwitz, J; Vierling, E; Carver, JA; Robinson, CV
    The function of ScHSP26 is thermally controlled: the heat shock that causes the destabilization of target proteins leads to its activation as a molecular chaperone. We investigate the structural and dynamical properties of ScHSP26 oligomers through a combination of multiangle light scattering, fluorescence spectroscopy, NMR spectroscopy, and mass spectrometry. We show that ScHSP26 exists as a heterogeneous oligomeric ensemble at room temperature. At heat-shock temperatures, two shifts in equilibria are observed: toward dissociation and to larger oligomers. We examine the quaternary dynamics of these oligomers by investigating the rate of exchange of subunits between them and find that this not only increases with temperature but proceeds via two separate processes. This is consistent with a conformational change of the oligomers at elevated temperatures which regulates the disassembly rates of this thermally activated protein. © 2010, Elsevier Ltd.