Role of hydrogen-bond network in energy storage of bacteriorhodopsin's light-driven proton pump revealed by ab initio normal-mode analysis.
Vibrational modes of the hydrogen-bond network in the binding site of bacteriorhodopsin (bR), a protein in halobacteria functioning as a light-driven proton pump, were investigated by an ab initio quantum mechanical/molecular mechanical (QM/MM) method. Normal-mode analysis calculations for O-D and N-D stretching modes of internal water molecules and the Schiff base of the retinal chromophore in the early intermediate state, K, reproduced well experimentally observed vibrational spectra. Supported by agreement with observed spectra, the QM/MM calculation suggests that weakened hydrogen bonds upon photoisomerization of the chromophore are an important means of energy storage in bR.
Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan.
Shigehiko
S
Hayashi
Emad
E
Tajkhorshid
Hideki
H
Kandori
Klaus
K
Schulten
D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D006860:Hydrogen Bonding; D008958:Models, Molecular; D011487:Protein Conformation; D017494:Proton Pumps / Q000737:chemistry* / Q000378:metabolism; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared; D013816:Thermodynamics
D017494:Proton Pumps; D001436:Bacteriorhodopsins