Rhodopsin halorhodopsin

Sensory rhodopsin (sR) and proteorhodopsin 4.12.1. Sensory rhodopsin Halobacteria contain a family of four retinal proteins, bR, halorhodopsin (hR), sensory rhodopsin I (sR I), and phobor-hodopsin (pR or sensory rhodopsin II, sR II), which carry two distinct functions through common photochemical reactions. In particular, bR... 

Halobacteria contain four rhodopsins bacteriorhodopsin, halorhodopsin, sensor-yrhodopsin, and phoborhodopsin (Fig. 4.2A) [11-17]. Bacteriorhodopsin and halorhodopsin are light-driven ion pumps, which act as an outward proton pump and an inward Ch pump, respectively. Sensoryrhodopsin and phoborhodopsin are photoreceptors that act to produce attractant and repellent responses in phototaxis, respectively. These four archaeal rhodopsins have similar structures seven helices constitute the transmembrane portion of the protein, and a retinal chromophore is bound to a lysine residue of the seventh helix via a protonated SchifF base linkage (Fig. 4.1). A negatively charged counterion is present to stabilize the positive charge inside the protein the counterion is an aspartate except for in halorhodopsin, which possesses a chloride ion. In sensoryrhodopsin, interaction with a transmembrane transducer protein raises the pKa of the aspartate, so that the aspartate is protonated at neutral pH. 

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... 

TABLE 124.1 List of microbial rhodopsins with database accession numbers. (BR bacteriorhodopsin, HR halorhodopsin, SRI II sensory rhodopsm I II, NR Neurospora rhodopsin, CSRA B Chlamydomonas sensory rhodopsm A B)... 

Bousche, O., Spudich, E.N., Spudich, J.L., and Rothschild, K.J., Conformational changes in sensory rhodopsin I similarities and differences with bacteriorhodopsin, halorhodopsin, and rhodopsin. 

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