TCB Publications - Abstract

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.

Download full text: PDF (482.9KB)