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Energy within the cell: Energy-saving chaperon Hsp90

Date:
January 13, 2012
Source:
Technische Universitaet Muenchen
Summary:
A special group of proteins, the so-called chaperons, helps other proteins to obtain their correct conformation. Until now scientists supposed that hydrolyzing ATP provides the energy for the large conformational changes of chaperon Hsp90. Now a research team has demonstrated that Hsp90 utilizes thermal fluctuations as the driving force for its conformational changes.

With their specially designed three-color single-molecule FRET (Foerster resonance energy transfer) assay with alternating laser excitation (ALEX) for simultaneous observation of ATP binding and conformational changes professor Hugel and his team could prov, that Hsp90 utilizes thermal fluctuations for its large conformational changes.
Credit: Christoph Ratzke

A special group of proteins, the so-called chaperones, helps other proteins to obtain their correct conformation. Until now scientists supposed that hydrolyzing ATP provides the energy for the large conformational changes of chaperone Hsp90. Now a research team from the Nanosystems Initiative Munich (NIM) could prove that Hsp90 utilizes thermal fluctuations as the driving force for its conformational changes.

The  journal PNAS reports on their findings.

ATP is the major energy source for most organisms and ATPases are the machines, which utilize this fuel, for example to move muscles or cargo in our body. The very abundant chaperone protein Hsp90 has such an ATPase in each of its two monomers. During the last years experiments had suggested that the movement and conformational changes of ATPase proteins are in general strictly linked to ATP binding and hydrolysis (i.e. fuel consumption).

To probe this theory Thorsten Hugel, Professor at the Technische Universitaet Muenchen (TUM) and member of the Nanosystems Initiative Munich (NIM), and his team designed a special three color single-molecule FRET (Fφrster resonance energy transfer) assay with alternating laser excitation (ALEX) for simultaneous observation of ATP binding and conformational changes. Unexpectedly the experiments revealed that binding and hydrolysis of ATP is not correlated with the large conformational changes of Hsp90. Hsp90 is instead a highly flexible machinery driven by thermal fluctuations.

"Thermal fluctuations are random changes in the structure of the protein -- they can be thought of as collisions with water molecules in the environment, which move rather violently at the temperatures in a living organism," says Thorsten Hugel. "Using these clashes to switch back and forth between different conformations, saves Hsp90 valuable ATP." But then what is the task of ATPase in the Hsp90 chaperone? The scientists suspect that co-chaperones and substrate proteins alter the system so that ATP binding or hydrolysis can take a crucial task.

With the newly developed experimental setup, it is now possible to investigate the very complex system in greater detail to resolve this important question. The Munich biophysicists therewith offer a new perspective on the energy conversion in molecular machines.

The work was supported by grants from the DFG (Hu997/9-1, SFB 863) and the Cluster of Excellence Nanosystems Initiative Munich (NIM) and the NanoBio-Technology program of the Elite Network of Bavaria.


Story Source:

The above story is based on materials provided by Technische Universitaet Muenchen. Note: Materials may be edited for content and length.


Journal Reference:

  1. C. Ratzke, F. Berkemeier, T. Hugel. Heat shock protein 90's mechanochemical cycle is dominated by thermal fluctuations. Proceedings of the National Academy of Sciences, 2011; 109 (1): 161 DOI: 10.1073/pnas.1107930108

Cite This Page:

Technische Universitaet Muenchen. "Energy within the cell: Energy-saving chaperon Hsp90." ScienceDaily. ScienceDaily, 13 January 2012. <www.sciencedaily.com/releases/2012/01/120113210612.htm>.
Technische Universitaet Muenchen. (2012, January 13). Energy within the cell: Energy-saving chaperon Hsp90. ScienceDaily. Retrieved April 18, 2014 from www.sciencedaily.com/releases/2012/01/120113210612.htm
Technische Universitaet Muenchen. "Energy within the cell: Energy-saving chaperon Hsp90." ScienceDaily. www.sciencedaily.com/releases/2012/01/120113210612.htm (accessed April 18, 2014).

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