Cooperative Assembly of Hsp70 Subdomain Clusters.

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Wright, Maya A 
Aprile, Francesco A  ORCID logo
Bellaiche, Mathias MJ 
Michaels, Thomas CT 
Müller, Thomas 

Many molecular chaperones exist as oligomeric complexes in their functional states, yet the physical determinants underlying such self-assembly behavior, as well as the role of oligomerization in the activity of molecular chaperones in inhibiting protein aggregation, have proven to be difficult to define. Here, we demonstrate direct measurements under native conditions of the changes in the average oligomer populations of a chaperone system as a function of concentration and time and thus determine the thermodynamic and kinetic parameters governing the self-assembly process. We access this self-assembly behavior in real time under native-like conditions by monitoring the changes in the micrometer-scale diffusion of the different complexes in time and space using a microfluidic platform. Using this approach, we find that the oligomerization mechanism of the Hsp70 subdomain occurs in a cooperative manner and involves structural constraints that limit the size of the species formed beyond the limits imposed by mass balance. These results illustrate the ability of microfluidic methods to probe polydisperse protein self-assembly in real time in solution and to shed light on the nature and dynamics of oligomerization processes.

Diffusion, Equipment Design, HSP70 Heat-Shock Proteins, Humans, Kinetics, Lab-On-A-Chip Devices, Protein Domains, Protein Multimerization, Thermodynamics
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American Chemical Society (ACS)
Alzheimer's Society (317 (AS-SF-16-003))
Biotechnology and Biological Sciences Research Council (BB/J002119/1)
European Research Council (337969)
The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013) through the ERC grant PhysProt (agreement no 337969) (T.P.J.K., M.A.W., and T.C.T.M.). In addition, we are grateful for financial support from the Frances and Augustus Newman Foundation (T.P.J.K. and M.A.W.), the Marie Curie Fellowship scheme (P.A.), the Cambridge Commonwealth, European and International Trust (M.M.J.B.), the NIH-Oxford Cambridge Scholars Programme (M.M.J.B.), St John’s College Cambridge (T.C.T.M.), the Swiss National Science Foundation (T.C.T.M.), and the Biotechnology and Biological Sciences Research Council (T.M.). F. A. A. is supported by a Senior Research Fellowship award from the Alzheimer’s Society, UK (grant number 317, AS-SF-16-003). This work was in part supported by the Intramural Research Program of the National Institute of Diabetes and Digestive and Kidney Diseases at the National Institutes of Health (M.M.J.B.) and the Centre for Misfolding Diseases, Cambridge, UK.