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Structure of bacteriorhodopsin at 1.55 A resolution.
H Luecke1, B Schobert, H T Richter
1Department of Molecular Biology and Biochemistry, University of California, Irvine, CA, 92697, USA.
Journal of Molecular Biology
|August 24, 1999
Summary
The atomic structure of bacteriorhodopsin, a light-driven ion pump, reveals a detailed hydrogen-bonded network involving water molecules. This network is crucial for the protein
Area of Science:
- Structural Biology
- Membrane Protein Biochemistry
- Biophysics
Background:
- Bacteriorhodopsin is a light-driven proton pump essential for energy transduction in Halobacterium salinarum.
- Understanding its atomic structure is key to elucidating its mechanism of action and the role of its lipid environment.
Purpose of the Study:
- To determine the high-resolution atomic structure of bacteriorhodopsin and its surrounding lipid matrix.
- To investigate the role of water molecules and lipid interactions in protein structure and function.
Main Methods:
- X-ray diffraction was used to analyze crystals of bacteriorhodopsin grown in a cubic lipid phase.
- Detailed structural analysis focused on protein residues, water molecules, and lipid interactions.
Main Results:
- An extensive three-dimensional hydrogen-bonded network involving protein residues and water molecules was identified in the extracellular region.
- A pi-bulge in transmembrane helix G, stabilized by water molecules, was observed near the retinal binding site.
- A lipid annulus of 18 tightly bound lipid chains surrounds the protein, mediating trimer contacts.
Conclusions:
- Bound water molecules play a significant role in both the structural integrity and functional mechanism of bacteriorhodopsin.
- The lipid matrix is integral to the stability and quaternary structure of the membrane protein complex.