Nanosecond structural dynamics of the chaperone Hsp90.

A complete understanding of protein function requires not only structural, but also dynamical information on a wide range of time scales. Large proteins present a particular challenge for nanosecond dynamics, as a comprehensive experimental investigation and an associated multi-scale understanding of how dynamics leads to function has not been established so far. In this study we not only determine these nanosecond dynamics for the multi-domain chaperone protein Hsp90, but also assign them to real-space movements and show that these dynamics can be modulated by a second protein. Our approach combines single-molecule fluorescence, quasi-elastic neutron scattering (QENS) and all-atom MD simulations. We observe molecular motions on the 100 ns time scale by nsFCS, which can be linked to full molecule-spanning dynamics consistently observed in QENS and MD simulations. Internal dynamics and global rotational diffusion are disentangled and attributed to specific displacements by combining nsFCS with time-resolved anisotropy and MD simulations. Finally, the effect of Sba1, a co-chaperone of Hsp90, shows that dynamics on these fast time scales is functionally important. Our integrative approach provides first insights into multi-domain protein dynamics on the nanoscale and encourages to extend the pure structure-function to a richer structure-dynamics-function paradigm also on the nanosecond time scale.