Cochaperones convey the energy of ATP hydrolysis for directional action of Hsp90

Abstract

The molecular chaperone and heat shock protein Hsp90 is part of many protein complexes in eukaryotic cells. Together with its cochaperones, Hsp90 is responsible for the maturation of hundreds of clients. Although having been investigated for decades, it still is largely unknown which components are necessary for a functional complex and how the energy of ATP hydrolysis is used to enable cyclic operation. Here we use single-molecule FRET to show how cochaperones introduce directionality into Hsp90’s conformational changes during its interaction with the client kinase Ste11. Three cochaperones are needed to couple ATP turnover to these conformational changes. All three are therefore essential for a functional cyclic operation, which requires coupling to an energy source. Finally, our findings show how the formation of sub-complexes in equilibrium followed by a directed selection of the functional complex can be the most energy efficient pathway for kinase maturation.

Constrained hidden Markov models reveal further Hsp90 protein states

“…I.e. it might be the state in which Hsp90 waits for the binding of nucleotides or cochaperones or clients to proceed towards other states [13].…”

“…Therefore, a transition between these four states is the current picture of the idle Hsp90 dimer, but more states could also describe these previous data. The four states have either been defined by the structural analogy between different Hsp90 homologues [4] or by a hidden Markov model (HMM) analysis of single-molecule FRET data [12,13] or Plasmon ruler data [14]. The HMM is a flexible tool that aims to infer undetected dynamics from partially available information [15][16][17].…”