Models bacteriorhodopsin

Fig. 5.4. Structure of the bacteriorhodopsin from Halobacterium halobium. Ribbon diagram of bacteriorhodopsin and retinal as a ball-and-stick model. Bacteriorhodopsin crosses the membrane with seven a-helices that are arranged in a bundle form with the chromophore retinal bound in the interior. According to Kimura et al. (1997), with per-...

Seki A, Kubo I, Sasabe H and Tomioka H 1994 A new anion-sensitive biosensor using an ion-sensitive field effect transistor and a light-driven chloride pump, halorhodopsin Appl. Biochem. Biotechnol. 48 205-11 Fuller B E, Okajima T L and Hong F T 1995 Analysis of the d.c. photoelectric signal from model bacteriorhodopsin membranes d.c. photoconductivity determination by means of the null current method and the effect of proton ionophores Bioelectrochem. Bioenerget. 37 109-24 Cone R A 1967 Early receptor potential photoreversible charge displacement in rhodopsin Science 155 1128-31... 

Michaile, S. and Hong, F.X, Component analysis of the fast photoelectric signal from model bacteriorhodopsin membranes. Part I. Effect of multilayer stacking and prolonged drying, Bioelectrochem. Bioenerg., 33,135, 1994. 

Henderson R, J M Baldwin, T A Ceska, F Zemlin, E Beckmann and K H Downing 1990. Model fo Structure of Bacteriorhodopsin Based on High-resolution Electron Cryo-microscopy. Joun Molecular Biology 213 899-929. 

Lanyi, J.K. Bacteriorhodopsin as a model for proton pumps. Nature 375 461-464, 1995. 

Henderson, R., et al. Model for the stmcture of bacteriorhodopsin based on high-resolution electron cryo-microscopy. /. Mol. Biol. 213 899-929, 1990. 

FIGURE 10.24 A helical wheel model of halorhodopsin. The amino acids facing the polar, hydrophilic core of the protein are shown. Of these 60 residues, 36 are conserved between halorhodopsin and bacteriorhodopsin. (Adapted from OesterMt, D., and Tittor, f, 1989. Treads ia Biochemical Scieaces 14 57—61.)... 

When Mitchell first described his chemiosmotic hypothesis in 1961, little evidence existed to support it, and it was met with considerable skepticism by the scientific community. Eventually, however, considerable evidence accumulated to support this model. It is now clear that the electron transport chain generates a proton gradient, and careful measurements have shown that ATP is synthesized when a pH gradient is applied to mitochondria that cannot carry out electron transport. Even more relevant is a simple but crucial experiment reported in 1974 by Efraim Racker and Walther Stoeckenius, which provided specific confirmation of the Mitchell hypothesis. In this experiment, the bovine mitochondrial ATP synthasereconstituted in simple lipid vesicles with bac-teriorhodopsin, a light-driven proton pump from Halobaeterium halobium. As shown in Eigure 21.28, upon illumination, bacteriorhodopsin pumped protons... 

For targets that lack structural information, such as GPCRs or ion channels, a pharmacophore model or multiple pharmacophore models for different series of compounds can explain SAR and guide the synthesis of new analogs. Alternatively, homology models based on bacteriorhodopsin have been used to explain the interactions of small molecules with GPCRs. 

Figure 2-3. Protonated Schiff-base of retinal (PSBR) and computational models used in ONIOM QM QM calculations (left). Electrostatic effects of the surrounding protein on excitation energies in bacteriorhodopsin evaluated using TD-B3LYP Amber right). (Adapted from Vreven and Morokuma [37] (Copyright American Institute of Physics) and Vreven et al. [38], Reprinted with permission.)...

F. T. Hong, The bacteriorhodopsin model membrane system as a prototype molecular computing element, BioSystems, 19, 223-236 (1986). 

Thus, the important question of the secondary structure of the transmembrane elements can only be addressed with models and by structural comparison with other transmembrane proteins for which the structure has been resolved. Detailed information on the structure of transmembrane elements is available for the photoreaction center of Rhodopseudomonas viridis (review Deisenhofer and Michel, 1989), cytochrome c oxidase (Iwata et al., 1995) and the OmpF porin of E. coli (Cowan et al., 1992 Fig. 5.3), amongst others. In addition, high resolution electron microscopic investigations and X-ray studies of bacteriorhodopsin, a light-driven ion pump with seven transmembrane elements, have yielded valuable information on the structure and configuration of membrane-spaiming elements (Henderson et al., 1990 Kimura et al., 1997 Pebay-Peyrula et al., 1997 Fig. 5.4). With the successful crystallization of the photoreaction center of Rhodopseudomonas viridis, a membrane protein was displayed at atomic resolution for the first time (Deisenhofer et al., 1985). The membrane-... 

The currently accepted structural models of the G-protein coupled receptor tend strongly towards the well established structure of bacteriorhodopsin (Fig. 5.4) that is also a 7-helix transmembrane protein. The model assumes that the seven helices are bedded bimdle-wise in the membrane. Detailed structural information on the conformation of the extracellular and intracellular structural portions is still lacking. 

A model for the structure of bacteriorhodopsin, a membrane protein from Halobacterium halobium. The protein has seven membrane-spanning segments connected by shorter stretches of hydrophilic amino acid residues. 

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