Evidence of alpha-helix slidings during bacteriorhodopsin photocycle-energetics coupling.
The three-dimensional structure of bacteriorhodopsin indicates that the all-trans-cis retinal bending causes alpha-helix slidings during the bacteriorhodopsin photocycle. For the elucidation of alpha-helix slidings taking place during the bacteriorhodopsin photocycle, we calculated ASAs of hydrophobic and hydrophilic atoms translocated by alpha-helix slidings with thermodynamic criteria found previously. Thermodynamic parameters calculated from ASAs (calculated delta Gtransfer and T delta S) were consistent with those (observed delta Gtransfer and T delta S) obtained empirically. These findings indicate that alpha-helix slidings take place during bacteriorhodopsin photocycle-energetics coupling. These mechanisms not only explain various phenomena, including some mutants forming a long-lived intermediate, but also predict various yet-unobserved phenomena, including the generation of heat in early photocycle intermediates.
Goto
K
K
Department of Pathology, Tohoku University School of Medicine, Sendai, Japan. kgoto@patholo2.med.tohoku.ac.jp
Iwamoto
M
M
D000595:Amino Acid Sequence; D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects*; D018360:Crystallography, X-Ray; D004735:Energy Transfer / Q000528:radiation effects; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010777:Photochemistry; D011485:Protein Binding / Q000528:radiation effects; D017433:Protein Structure, Secondary / Q000528:radiation effects*; D012172:Retinaldehyde / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects; D013329:Structure-Activity Relationship; D013816:Thermodynamics
D001436:Bacteriorhodopsins; D012172:Retinaldehyde