using-three-color-single-molecule-fret-to-study-correlation-protein

Using Three-color Single-molecule FRET to Study the Correlation of Protein Interactions

Single-molecule F&#246;rster resonance energy transfer (smFRET) has become a widely used biophysical technique to study the dynamics of biomolecules. For ...

University of Freiburg

We present an approach that enables us to simultaneously access structure and dynamics of a multidomain protein in solution. Dynamic domain arrangements are experimentally determined by combining self-consistent networks of distance distributions with known domain structures. Local structural dynamics are correlated with the global arrangements by analyzing networks of time-resolved single-molecule fluorescence parameters. The strength of this hybrid approach is shown by an application to the flexible multidomain protein Hsp90. The average solution structure of Hsp90's closed state resembles the known X-ray crystal structure with Angstrom precision. The open state is represented by an ensemble of conformations with interdomain fluctuations of up to 25 Å. The data reveal a state-specific suppression of the submillisecond fluctuations by dynamic protein-protein interaction. Finally, the method enables localization and functional characterization of dynamic elements and domain interfaces.

Multidomain structure and correlated dynamics determined by self-consistent FRET networks.

The function of the molecular chaperone Hsp90 depends on large conformational changes, the rearrangement of local motifs, and the binding and hydrolysis of ATP. The size and complexity of the Hsp90 system impedes the detailed investigation of their interplay using standard methods. To overcome this limitation, we developed a three-color single-molecule FRET assay to study the interaction of Hsp90 with a fluorescently labeled reporter nucleotide in detail. It allows us to directly observe the cooperativity between the two nucleotide binding pockets in the protein dimer. Furthermore, our approach disentangles the protein conformation and the nucleotide binding state of Hsp90 and extracts the kinetics of the state transitions. Thereby, we can identify the kinetic causes mediating the cooperativity. We find that the presence of the first nucleotide prolongs the binding of the second nucleotide to Hsp90. In addition, we observe changes in the kinetics for both the open and the closed conformation of Hsp90 in dependence on the number of occupied nucleotide binding sites. Our analysis also reveals how the co-chaperone Aha1, known to accelerate Hsp90's ATPase activity, affects those transitions in a nucleotide-dependent and independent manner, thereby adding another layer of regulation to Hsp90.

Article	Year
Multidomain structure and correlated dynamics determined by self-consistent FRET networks. Nature methods\| PubMed ID: 27918541	2017
Cooperative Nucleotide Binding in Hsp90 and Its Regulation by Aha1. Biophysical journal\| PubMed ID: 29045865	2017

Philipp Wortmann

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