Details of the Conformational Cycle of Hsp90 Probed using Optical Tweezers

Abstract

Heat shock protein 90 (Hsp90) is an ATP-driven molecular chaperone which is essential in eukaryotes. It functions as a part of a number of complexes with many different co-chaperone proteins, which regulate its conformational cycle [1]. Using a custom-built single molecule optical trapping experimental setup, we have previously elucidated the mechanism by which this large protein folds [2], characterised the role of its flexible charged linker region [3], performed a detailed comparison of Hsp90 orthologs [4] and elucidated details of its dimerization dynamics [5]. Hsp90 is known to exist in two forms in yeast – the constitutively expressed Hsc82 and the form that is upregulated under cellular stress conditions, Hsp82 [6]. We recently performed a detailed comparison of these two isoforms, using a broad range of biophysical techniques to compare their function, structural properties and interactomes. Despite a 97% sequence similarity, we find significant differences in their stabilities, folding and conformational regulation [7]. We are currently working towards developing a complete quantitative description of the conformational cycle of Hsp82, as driven by co-chaperone proteins, nucleotides and clients using single molecule optical tweezers combined with standard biochemical techniques. [1] F. H. Schopf, M. M. Biebl & J. Buchner, Nat. Rev. Mol. Cell Biol. 18, 345 – 360, (2017). [2] M. Jahn, et al. Proc. Nat. Acad. Sci. 113, 1232–1237, (2016). [3] M. Jahn, et al. Proc. Nat. Acad. Sci. 111, 17881–17886, (2014). [4] M. Jahn and K. Tych, et al. Structure 26, 96 – 105, (2018). [5] K. Tych et al. J. Phys. Chem. B 122, 11373-11380 (2018). [6] K.A. Borkovic et al. Mol. Cell. Biol. 9, 3919 – 3930, (1989) [7] H. Girstmair and F. Tippel, et al. Nature Comms. 10, 1 – 15 (2019).