Rhodopsins photolysis

Fukada Y, Yoshizawa T (1981) Activation of phosphodiesterase in frog rod outer segments by an intermediate of rhodopsin photolysis. II. Biochim Biophys Acta 675 195-200... 

Lewis, J.W., Winterle, J.S., Powers, M.A., Kliger, D.S., and Dratz, E.A., Kinetics of rhodopsin photolysis intermediates in retinal rod disk membranes. I. Temperature dependence of lumirhodopsin and metarhodopsin I kinetics, Photochem. Photobiol, 34, 375, 1981. 

Shevchenko, T.F., Kalamkarov, G.R., and Ostrovsky, M.A., The lack of H transfer across the photoreceptor membrane during rhodopsin photolysis. Sensory Systems (USSR Acad. Sci.), 1,117, 1987 (in Russian). 

I and II. At very low temperatures a transient form photorhodopsin with a wavelength maximum at 580 nm may precede bathorhodopsin.461b,501-502a Furthermore, nanosecond photolysis of rhodopsin has revealed a blue-shifted intermediate that follows bathorhodopsin within 40 ns and decays into lumirhodopsin.500,503,504 The overall result is the light-induced isomerization of the bound 11-czs-retinal to all-fraus-retinal (Eq. 23-38) and free opsin. Tire free opsin can then combine with a new molecule of 11-czs-retinal to complete the photochemical cycle. 

Fig. 5. (A) Bleaching intermediates in the photolysis of bovine rhodopsin extracts. Adapted from Yoshizawa and Horiuchi [61]. (B) Bleaching intermediates in the photolysis of squid rhodopsin extracts. Adapted from Shichida et al. [105]. Photoreactions are symbolized by wavy lines, thermal reactions by straight lines.

In spite of the differences in the behavior of the pigments, in situ, as compared to extracts, studies on extracts provide useful information, not only on the structure of the bleaching intermediates, but also on the possible roles they may be playing in the photoreceptors. The bleaching intermediates from several species have been investigated extensively by using flash photolysis techniques and both low temperature and ultrafast kinetic spectroscopy. As an example, Fig. 5 shows the sequence of the intermediates in the photolysis of bovine and squid rhodopsin extracts. 

Low temperature experiments have shown the formation of hypso intermediates from several species [99,103,105-107]. The study of early photoconversion processes in squid [108], which also involved the evaluation of the relative quantum yields among the four pigments (squid rhodopsin, squid batho-, hypso- and isorhodopsin) showed that hypsorhodopsin is a common intermediate of rhodopsin and isorhodopsin there is no direct conversion between rhodopsin and isorhodopsin bathorhodopsin is not converted directly to hypsorhodopsin and both rhodopsin and isorhodopsin convert more efficiently to bathorhodopsin than to hypsorhodopsin. While a temperature dependence of the relaxation processes from the excited state of rhodopsin, and an assumption that batho could be formed from one of the high vibrational levels of the ground state hypso have been invoked to explain these findings [108], the final clarification of this matter awaits results from subpicosecond laser photolysis experiments at liquid helium temperature. 

Fig. 14. a Protonated Schiff bases of ail-trans and 11-cis retinal, b Sequence of intermediates in the photolysis of rhodopsin. The absorption maximum of each intermediate is shown in parenthesis 651... 

Jager S, Lewis JW, Zvyaga TA, Szundi I, Sakmar TP, Kliger DS. Chromophore structural changes in rhodopsin from nanoseconds to microseconds following pigment photolysis. Proc Natl Acad Sci USA 1997 94 8557-8562. 

The first challenge to the isomerization model was made in 1972 by picosecond laser photolysis [34], The first picosecond laser photolysis observed formation of bathorhodopsin within 6 ps after excitation of bovine rhodopsin at room tempera-... 

The regeneration capacity of rhodopsin, defined as the amount of rhodopsin (in precent of the original amount) obtained after photolysis and reaction with excess 11-cis retinaldehyde, is 92% for native photoreceptor membranes (Table II, 3rd column). This parameter is very sensitive to detergent action. It is reduced to zero in preparations solubilized in DTAB (100 mM), but can recover nearly fully upon reconstitution with phospholipids and removal of detergent by dialysis. 

Nishioku, Y., Nakagawa, M., Tsuda, M., Terazima, M. Energetics and volume changes of the intermediates in the photolysis of octopus rhodopsin at physiological temperature. Biophys. J. 83, 1136-1146 (2002)... 

Shichida, Y, Matuoka, S., and Yoshizawa, T., Formation of photorhodopsin, a precursor of bath-rhodopsin, detected by a picosecond laser photolysis at room temperature, Photochem. Photobiol.,... 

Mao, B., Tsuda, M., Ebrey, T.G., Akita, H., Balogh-Nair, V., and Nakanishi, K., Flash photolysis and low temperature photochemistry of bovine rhodopsin with a fixed 11 -ene, Biophys.., 35,543,... 

Mizukami, T., Kandori, H., Shichida, Y, Chen, A.H., Derguini, E, Caldwell, C.G., Biffe, C.F., Nakanishi, K., and Yoshizawa, T., Photoisomerization mechanism of the rhodopsin chromophore picosecond photolysis of pigment containing 11 -cis-locked eight-membered ring retinal, Proc. Natl. Acad. Sci. USA, 90, 4072, 1993. 

Several of the techniques used to measure the stoichiometry of the protonation changes were also used to measure the time course with which the proton is taken up during the photolysis of rhodopsin. With measurements taken in ROS membranes or rhodopsin in digitonin, it was found that proton uptake fairly well matched the Meta-I-to-Meta-II transition rate, although resolution and precision were limited. Bennett reported good time resolution data for proton uptake (bromocresol purple) and Meta II formation (absorbance at 365 nm), and found that they matched. Kaupp et al. used the pH indicator bromocresol purple to show that in sonicated ROS membranes, proton uptake and Meta II formation times were identical at 20°C. 

Thorgeirsson, T.E., Lewis, J.W., Wallace-Williams, S.E., and KKger, D.S., Photolysis of rhodopsin results in deprotonation of its retinal Schiff s base prior to formation of metarhodopsin II, Pho-tochem. Photobiol, 56, 1135, 1992. 

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