Bacterial rhodopsins

Eubacteria Eubacteria Archeobacteria Anoxygenation Oxygenation Halogen arion Bacterial chlorophyll Chlorophylls Bacterial rhodopsin Hj, HoS. S. Oiganics H20,H2S Do not participate ATP + NO, D, P(H) ATP + NO, D. P(H1 ATP CO2 + Organics CO2 + Organics Organics... 

D 2D space group (2D crystal) p3 Bacterial rhodopsin membrane 11... 

This review will descrihe recent advances, as well as current views and controversies, rather than give an exhaustive account of the vast literature of the bacterial rhodopsins. For the latter, and for aspects not covered here, the reader should consult the numerous earlier and more specialized reviews [1-7]. 

In free retinal, illumination will produce a mixture of several single- and doublebond isomeric configurations. Protein-bound retinal is more restricted in its motional possibilities in the rhodopsins the binding pocket is tailored to fit only a few specific retinal configurations. Indeed, the light-initiated reaction cycles of the bacterial rhodopsins are based exclusively on dlX-trans to 13-cw isomerization of their retinal chromophores. When under some conditions other isomers are produced upon illumination, such as 9 cis, they accumulate in limited quantities [90-92]. 

This is certainly a very interesting problem, and it is feasible to examine such a tetramer by our computational methods. However, simply because one does not have enough time to work on all interesting problems, we have decided to concentrate on a related problem - and that is the structure of bacterial rhodopsin. Since this protein presumably consists of seven packed a-helices, we hope to be able to apply our methodology for treating assemblies of a-helices to the rhodopsin-structure problem. 

A representation of the key experiment proving the chemiosmotic hypothesis. At the bottom is the lightactivated electrogenic proton pump, bacterial rhodopsin, and on the top the F,Fo ATP synthase. When light is shone on the vesicles coreconstituted with these two pumps in the presence of ADP and inorganic phosphate (Pi), ATP synthesis was observed. The only linkage between the two sets of structures is the electrochemical gradient of protons induced by illumination. 

Biofuel industry is one of the upcoming industries who are in search of new and different strategies for the conversion of biomass into biofuel products. Since Archaea are exposed to strict sunlight, they have adapted a mechanism to convert solar energy by the transversion of protons and chloride ions for phototaxis. They harbor light sensitive proteins called the bacterial rhodopsin, a 25 kDa protein that carries the retinal group linked to lysine-216 by the Schififbase action. The bacteriorhodopsin protein is used in holography, spatial modulators, artificial retina and volumetric and associative optical memories (Alqueres et al., 2007). 

Opsin, which loops back and forth across the cell membrane, and rhodopsin are transmembrane proteins. Unwin and Henderson used electron microscopy to determine the structure of bacterial rhodopsin at 7 A resolution. More recently, the crystal structure of bovine rhodopsin at 2.8 A resolution was solved by Palczewski and colleagues. 

Seven transmembrane helices (7-TM) are a stmctural motif common to a large family of photo- and chemoreceptor proteins. Most prominent examples of 7-TM proteins include (bacterial) rhodopsins and G protein-coupled receptors (GPCRs). 

More recently several other bacterial rhodopsins such as proteorhodopsin and Anabaena sensory rhodopsin (ASR) have been investigated with solid-state NMR. Remarkable spectral resolution and sensitivity resulting in nearly complete resonance... 

Microbial Rhodopsins Archaeal Rhodopsins Bacterial Rhodopsins Eukaryotic Rhodopsins. 124-2... 

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