Photo-Rhodopsin

S., Grzesiek, S., litman, B. J., Bax, A. Measurement of dipolar couplings in a transdudn peptide fragment weakly bound to oriented photo-activated rhodopsin. f. Biomol. NMR 2000, 16, 121-125. 

Intriguingly, the conical intersection model also suggests that E,Z-isomerization of acyclic dienes might be accompanied by conformational interconversion about the central bond, reminiscent of the so-called Hula-Twist mechanism for the efficient ,Z-photo-isomerization of the visual pigment rhodopsin in its rigid, natural protein environment101. A study of the photochemistry of deuterium-labelled 2,3-dimethyl-l,3-butadiene (23-d2) in low temperature matrices (vide infra) found no evidence for such a mechanism in aliphatic diene E,Z -photoisomerizations102. On the other hand, Fuss and coworkers have recently reported results consistent with the operation of this mechanism in the E,Z-photoisomerization of previtamin D3 (vide infra)103. 

Photosynthetic prokaryotes do not have chloroplasts. Their photosynthetic pigments are embedded in their cell walls. Some use bacteriochlorophyll for light harvesting. In the proteobacteria and archaea, light harvesting is accomplished by the protein rhodopsin, which acts as a photo-driven proton pump that fuels phosphorylation of ADP. 

In connection with the problem of oscillations discussed by previous speakers and other types of dynamical behavior of membranes, it would probably be timely to mention here in some more detail the experiments with vision rhodopsin that were performed in our institute by using the Mossbauer spectroscopy method [G. R. Kalamkarov et al., Doklady Biophys., 219, 126 (1974)]. These experiments manifested the existence of reversible photo-induced conformational changes in the photoreceptor membrane even at such low temperature as 77°K. We have labeled various samples of solubilized rhodopsin and of photoreceptor membranes by iron ascorbate enriched with Fe57 and looked for the change of Mossbauer spectra caused by the illumination of our samples. 

S ATP -I- 338-SKTETSQVAPA-348 <1, 12> (<1, 12> peptide containing the last 11 amino acids of the C-terminal of bovine rhodopsin [20, 24] <1> phosphorylated at Ser-343, about 11% of the rate with rhodopsin, photo-activated rhodopsin-dependent, soluble active kinase catalyzes photoacti-vated rhodopsin-independent peptide phosphorylation [20] <12> only in the presence of photoactivated rhodopsin, which activates RK for peptide phosphorylation, also activated by metarhodopsin III, but not by opsin, up to 60% of the rate with photoactivated rhodopsin, light-dependent phosphorylation [24]) (Reversibility <1,12> [20,24]) [20, 24]... 

ATP -I- peptide <1> (<1> monophosphorylated [7] <1> containing sites phosphorylated in rhodopsin [9, 23] <1> less amount of phosphoryl group incorporation than of rhodopsin [9] <1> corresponding to the C-terminus and loop 5-6 of opsin, poor substrates, phosphorylates serine and threonine residues in each peptide [12] <1> acid-rich peptides, RK prefers acid residues localized to the C-terminal side of the serine [15, 23] <1> low catalytic efficiency of RK toward a peptide containing its major autophosphorylation site [27] <1> acidic peptides, stimulated by photo-lyzed rhodopsin, K-491 of RK participates in substrate binding [33]) (Reversibility <1> [7, 9, 12, 15, 22, 23, 27, 33, 36]) [7, 9, 12, 15, 22, 23, 27, 33, 36]... 

A great deal of fundamental information about vision has been obtained through absorption spectroscopy. 6) The primary event in vision is the photo-chemical formation of bathos rhodopsin from rhodopsin and isorhodopsin. Rhodopsin is the... 

Our retina has red, green, and blue cones which include rhodopsins as photoreceptors [6-8], Phytochromes are photo-sensors of green plants [9], Biological luminescences from fireflies [10] and some jellyfishes [11] are also beautiful activities of living organism. Recently, fluorescent proteins are routinely applied as molecular markers for gene expression in the field of molecular biology [12]. 

Intermolecular Photo-Induced Electron Transfer. Picosecond absorption spectroscopy has also been applied recently to studies of intermolecular electron transfer on the picosecond time scale.(34) As in the previously described study of rhodopsin, the photo-induced intermolecular electron transfer between chloranil (CHL) and the arenes, naphthalene (NAP), 9,10-dihydrophenanthrene (DHP), and indene (IN) was studied by means of picosecond absorption spectroscopy which utilizes an OMCD. Difference absorption spectra of samples of CHL and one of these particular arenes in acetonitrile were measured at selected delay times after excitation at 355-nm with 25-ps FWHM laser pulses. These picosecond spectroscopic studies revealed information about the mechanism of intermolecular electron transfer and subsequent radical ion formation that was not possible in previous spectroscopic studies performed on the nanosecond (35-37) and microsecond (38,39) time scales. 

Photo-activated retina rhodopsin, a G-protein coupled receptor (GPCR), is a major component in purple membranes (PM). Due to the high structural content of helices in GPCR, GPCR rich PM disks align in the presence of a magnetic field... 

In the biochemistry of vision (see Chapter 17), the interaction of rhodopsin, a GCPR, with light results in the photo-induced isomerization of cis retinal imine to trans retinal imine. This causes conformational changes in rhodopsin, which ultimately result in the closing of an ion channel, polarization of the cell membrame, and a nerve impulse that is transmitted to the brain in vision. 

In mammals, (1IZ)-Retinal, generated from retinol in the retina, is the photo-reactive chromophore, which forms a Schiff-base to a lysine residue of opsin, a G-protein-coupled receptor (GPCR) protein, to give rhodopsin. This visual purple is concentrated in the outer parts of the rod and cone photoreceptors. Upon light absorption, the chromophore converts photons into a chemical signal by isomerisation to (all )-retinal, which causes a conformational change of... 

---