Conformational Changes of Hsp104 Revealed through Small Angle X-Ray Scattering (SAXS)

Abstract

Hsp104 is a hexameric AAA+ disaggregase found in yeast. Hsp104 has two key roles in vivo; thermotolerance and the regulation of prions. After thermal or chemical stress Hsp104 has the ability, in collaboration with co-chaperones Hsp40 and Hsp70, to remodel cytosolic aggregates and return proteins to their soluble, native form. Its role in prion regulation is two- fold. In yeast, prions function as non-genetic heritable traits. Hsp104 is required for prion propagation from mother to daughter through nucleation and fiber fragmentation, but cures some prion phenotypes when overexpressed.Hsp104 is a large, multidomain protein. Each monomer contains two AAA+ domains resulting in an oligomeric species containing 12 sites of ATP hydrolysis. To date, there are no high resolution structures of either monomeric or hexameric Hsp104, and little is known about how the protein changes in shape during the ATPase cycle and how it uses these changes to exert remodeling forces on a variety of substrates.Here I present ongoing work that uses an in solution technique, SAXS, to study the conformational changes of the Hsp104 hexamer during the ATPase cycle. SAXS studies are well suited to the Hsp104 system due to the large size of the particle, the large available yield after purification, the monodispersity of the hexamer and the large changes that take place in the presence of different nucleotides.