Biology subjects

Baldwin, A. J.

Publications and source records attributed to Baldwin, A. J..

2 recordsLinked to original sources

bioRxiv2018

Local unfolding of the HSP27 monomer regulates chaperone activity

The small heat-shock protein HSP27 is a redox-sensitive molecular chaperone that is expressed throughout the human body. Here we describe redox-induced changes to the structure, dynamics, and function of HSP27 and its conserved -crystallin domain, and provide the first structural characterization of a small heat-shock protein monomer. While HSP27 assembles into oligomers, we show that the transiently populated monomers released upon reduction are highly active chaperones in vitro, but are kinetically unstable and susceptible to uncontrolled aggregation. By using relaxation dispersion and high-pressure nuclear magnetic resonance spectroscopy, we reveal that the pair of {beta}-strands that mediate dimerization become partially disordered in the monomer. Strikingly, we note that numerous HSP27 mutations associated with inherited neuropathies cluster to this unstructured region. The high degree of sequence conservation in the -crystallin domain amongst mammalian sHSPs suggests that partially unfolded monomers may be a general, functional feature of these molecular chaperones.

biophysics↗

bioRxiv2018

αB-crystallin inhibits amyloidogenesis by disassembling aggregation nuclei

Amyloid formation is implicated in a range of neurodegenerative conditions including Alzheimers and Parkinsons diseases. The small heat-shock protein B-crystallin (BC) is associated with both, and directly inhibits amyloid formation in vitro and its toxicity in cells. Studying the mechanism of aggregation inhibition is challenging owing to sample heterogeneity and the dynamic nature of the process. Here, by means of NMR spectroscopy and chemical kinetics, we establish the mechanism by which the protein -lactalbumin aggregates and forms amyloid, and how this is inhibited by BC. In particular, we characterise the lifetime of the unstable aggregation nucleus, and determine that this species is specifically destabilised by BC. This mechanism allows the chaperone to delay the onset of aggregation, although it is overwhelmed on longer timescales. The methodology we present provides a mechanistic understanding of how BC reduces the toxicity of amyloids, and is widely applicable to other complex mixtures.

biophysics↗