Shigehiko Hayashi, Emad Tajkhorshid, and Klaus Schulten.
Structural changes during the formation of early intermediates in the
bacteriorhodopsin photocycle.
Biophysical Journal, 83:1281-1297, 2002.
(PMC: 1302228)
HAYA2002
Early intermediates of bacteriorhodopsin's photocycle
were modeled by means of ab initio quantum
mechanical/molecular mechanical (QM/MM) and
molecular dynamics (MD) simulations. The
photoisomerization of the retinal chromophore and the
formation of photoproducts corresponding to the early
intermediates were simulated by MD simulations. By
means of the QM/MM method, the resulting structures
were refined and the respective excitation energies
were calculated. Two sequential intermediates were
found with absorption maxima that exhibit red-shifts
from the resting BR state. The intermediates were
therefore assigned to the K and KL states. In K, the
conformation of the retinal chromophore is strongly
deformed, and the N-H bond of the Schiff base points
almost perpendicular to the membrane normal toward
Asp212. The strongly deformed conformation of the
chromophore and weakened interaction of the Schiff
base with the surrounding polar groups are the means
by which the absorbed energy is stored. During the
K-to-KL transition, the chromophore undergoes further
conformational changes that result in the formation of a
hydrogen bond between the N-H group of the Schiff
base and Thr89, as well as other rearrangements of
the hydrogen-bond network in the vicinity of the
Schiff base, which are suggested to play a key role in
the proton transfer process in the later phase of the
photocycle.
Download Full Text
The manuscripts available on our site are provided for your personal
use only and may not be retransmitted or redistributed without written
permissions from the paper's publisher and author. You may not upload any
of this site's material to any public server, on-line service, network, or
bulletin board without prior written permission from the publisher and
author. You may not make copies for any commercial purpose. Reproduction
or storage of materials retrieved from this web site is subject to the
U.S. Copyright Act of 1976, Title 17 U.S.C.
