Functional waters in intraprotein proton transfer monitored by FTIR difference spectroscopy
Florian Garczarek1, Klaus Gerwert
1Lehrstuhl für Biophysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
Nature
|November 11, 2005
Summary
This study reveals how bacteriorhodopsin uses specific water arrangements for controlled proton transfer, unlike random migration in liquid water. Intraprotein water is crucial for biological functions.
Area of Science:
- Biophysics
- Structural Biology
- Spectroscopy
Background:
- Extensive research exists on water molecule reactions and proton transfer in bulk liquids and gas-phase clusters.
- However, the role and behavior of individual water molecules within heterogeneous proteins during enzymatic reactions remain less understood.
Purpose of the Study:
- To elucidate the mechanism by which the membrane protein bacteriorhodopsin facilitates proton transfer.
- To investigate the specific roles of intraprotein water molecules, including hydrogen-bonded networks and protonated clusters, in this process.
Main Methods:
- Utilized time-resolved Fourier transform infrared spectroscopy (trFTIR).
- Employed in situ H2(18)O/H2(16)O exchange FTIR for isotopic labeling and analysis.
Main Results:
- Identified a precise arrangement of water molecules within bacteriorhodopsin.
- Demonstrated the interplay of strongly hydrogen-bonded water, a water molecule with a dangling hydroxyl group, and a protonated water cluster.
- Showcased controlled Grotthuss proton transfer within the protein matrix.
Conclusions:
- The specific organization of water molecules in bacteriorhodopsin enables controlled proton transfer, distinct from random migration in liquid water.
- Intraprotein water molecules are demonstrated to be essential for biological functions, comparable to amino acids.
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