Retinal proteins bacteriorhodopsin

Hayashi, S., Tajkhorshid, E., Pebay-Peyroula, E., Royant, A., Landau, E. M., Navarro, J., 8c Schulten, K. (2001). Structural determinants of spectral tuning in retinal proteins-bacteriorhodopsin vs sensory rhodopsin II. The Journal of Physical Chemistry B, 105(41), 10124-10131. 

Hampp, N. (2000) Bacteriorhodopsin as photochromic retinal protein for optical memories. Chemical Reviews, 100, 1755-1776. 

Another study45 used the 2H 7jz anisotropy of CD3 groups in 6-5-civ-retinoic acid, in 6-5-frans-retinoic acid (Fig. 16a) and in the membrane protein bacteriorhodopsin regenerated with CD3-labelled retinal (Fig. 16b) to examine the motion of the CD3 groups. It was found that for both forms of retinoic acid, a three-site hopping model fitted the experimental data, but with the difference that the activation energy for the cis isomer was 14.5 1 kJmol-1 whereas for the... 

Photoreceptor Pigments. There have been several reviews on the structures, photochemistry, and functioning of the retinal-protein photoreceptor pigments involved in the processes of visionand in the purple membrane of Halobacteria (bacteriorhodopsin). ° ° In addition to the papers quoted earlier on the spectroscopy of these pigments, many other reports have appeareddealing with rhodopsin and intermediates in its photocycle, especially photochemistry, chromophore-protein conformation and binding, and reaction kinetics. Similar studies on bacteriorhodopsin have also been described." "-"" ... 

Bacteriorhodopsin and halorhodopsin are unique energy transducers characteristic of halobacteria and absent in other living cells. The structural and functional aspects of these retinal proteins will be considered in Chapter 6 of this volume. Here we would like to review only two aspects of the problem, namely, the mechanism of the light-induced transmembrane eharge displacement by bacteriorhodopsin, and the involvement of bacteriorhodopsin in photoreception, mediated by a sensor. 

When bacteriorhodopsin was discovered in 1971, its similarity to the visual rhodopsin in the chromophore structure (retinal), the primary light-induced event (retinal isomerization) and the photocycle (short-wavelength intermediate formation) impelled the authors to suggest that this novel retinal protein is somehow involved in photoreception [1]. Such a suggestion seemed reasonable since halobacteria are known to change their direction of swimming in response to a light stimulus. 

However, subsequent studies on halobacterial retinal proteins seemed to argue against the photoreceptor function of bacteriorhodopsin. It was found that (i) bacteriorhodopsin operates as a light-driven H pump and (ii) in the same halobacteria there are two other retinal proteins, i.e., sensory rhodopsin I and sensory rhodopsin II (also known as photorhodopsin) which are specialized in photoreception rather than in H pumping, being present in much smaller amounts than bacteriorhodopsin [36-43]. It was shown that... 

The retinal proteins of halobacteria constitute a unique set of light energy transduction devices, based on similar chemistry but designed to perform different functions. The contributions of bacteriorhodopsin to our understanding of the structure and function of membrane proteins have been, and will no doubt continue to be, spectacular. As descriptions of the properties of the other two halobacterial retinal pigments are now becoming available, they promise to provide further insights into how membrane proteins function. 

The first protein to be comprehensively studied by solid state NMR was the robust membrane protein bacteriorhodopsin, as it could be readily reconstituted with specifically labelled retinal. For example, Griffin and coworkers deduced the conformation of the chromophore from its isotropic N and... 

Fig. 23. (A) The halophilic bacterium H. halobium with patches containing the "purple membrane" (B) Structure of the protein bacteriorhodopsin (left) and the structural formula for the chromophore retinal (right) (C) Covalent binding of retinal with iysine-216 forming a positively-charged Schiff base (D) Illumination of the bacteriorhodopsin retinal and transformation from a trans- to a cis-configuration and releases a proton from the Schiff base to the cell exterior relaxation to ttie trans-form, with uptake of a proton from the cytoplasmic interior. The combination of deprotonation and reprotonation on opposite sides of the membrane constitutes a proton pump. See text for other details. Figures partly adapted from Becker and Deamer (1991) The World of the Cell (2nd ed) Benjamin/Cummings PubI Co. p 215.

Stryer L 1986 Cyclic GMP cascade of vision Anna. Rev. Neurosci. 9 87-119 Cafiso D S and Hubbell W L 1980 Light-induced interfacial potentials in photoreceptor membrane Biophys. J. 30 243-63 Drain C M, Christensen B and Mauzerall D 1989 Photogating of ionic currents across a lipid bilayer Proc. Natl Acad. Sci. USA 86 6959-62 Vsevolodov N N, Druzhko A B and Djukova T V 1989 Actual possibilities of bacteriorhodopsin application Molecular Electronics Biosensors and Biocomputers ed F T Hong (New York Plenum) pp 381-4 Vsevolodov N N and Dyukova T V 1994 Retinal-protein complexes as optoelectronic components Trend. Biotechnol. 12 81-103 Vsevolodov N N, Djukova T V and Druzhko A B 1989 Some methods for irreversible write-once recording in Biochrom films Proc. Annu. Int. Conf IEEE Eng. Med. Biol. Soc. 11 1327... 

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