To regenerate light-sensitive rhodopsin in rods from active metarhodopsin II (Meta II), all-trans-retinal must be removed from the retinal binding pocket and metabolically supplied 11-cis-retinal has to form a new retinylidene bond in the active site. Recent work from this laboratory has focused on Meta II decay and release and uptake of retinals in opsin employing intrinsic protein fluorescenc...

We report that the light-activated bovine metarhodopsin II, upon decay, first forms opsin in the correctly folded form. The latter binds 11-cis-retinal and regenerates the native rhodopsin chromophore. However, when the opsin formed upon metarhodopsin II decay is kept in 0.1% dodecyl maltoside, it converts in a time-dependent manner to a form(s) that does not bind 11-cis-retinal. On subsequent ...

BACKGROUND AND OBJECTIVES Halophilic bacteria produce a variety of pigments, which function as immune modulators and have prophylactic action against cancers. In this study, colorful halophilic bacteria were isolated from solar salt lake and their pigments was extracted in optimal environmental conditions and compared with the pigments of Halorubrum sodomense ATCC 33755. MATERIALS AND METHODS...

Surface plasmon resonance (SPR) spectroscopy has been used to follow incorporation and light-induced conformational changes in bovine rhodopsin reconstituted into an egg phosphatidylcholine bilayer deposited on a thin silver film. The magnitude of the SPR spectral changes caused by light varies with pH in a manner paralleling that in flash photolysis experiments, which monitor formation of meta...

Thermal activation of the visual pigment constitutes a fundamental constraint on visual sensitivity. Its electrical correlate in the membrane current of dark-adapted rods are randomly occurring discrete "dark events" indistinguishable from responses to single photons. It has been proposed that thermal activation occurs in a small subpopulation of rhodopsin molecules where the Schiff base linkin...

To clarify the formation process of acid metarhodopsin in the cephalopod rhodopsin cycle, changes in the difference spectrum of squid (Todarodes pacificus) rhodopsin in acid (pH 5.7, or pH 6.1) and alkaline (pH 10.2) solutions were studied at various temperatures by applying the flash photolytic technique. An intermediate with an absorption maximum at about 475 nm was transformed from lumirhodo...

The changes that lead to activation of G protein-coupled receptors have not been elucidated at the structural level. In this work we report the crystal structures of both ground state and a photoactivated deprotonated intermediate of bovine rhodopsin at a resolution of 4.15 A. In the photoactivated state, the Schiff base linking the chromophore and Lys-296 becomes deprotonated, reminiscent of t...

Discrepancies exist among spectral measurements of sensitivity of crayfish photoreceptors, their absorption in situ, and the number and absorption spectra of crayfish photopigments that are extracted by digitonin solutions. We have determined the photosensitivity spectrum of crayfish rhodopsin in isolated rhabdoms using long wavelength fluorescence emission from crayfish metarhodopsin as an int...

Discrepancies exist among spectral measurements of sensitivity of crayfish photoreceptors, their absorption in situ, and the number and absorption spectra of crayfish photopigments that are extracted by digitonin solutions. We have determined the photosensitivity spectrum ofcrayfish rhodopsin in isolated rhabdoms using long wavelength fluorescence emission from crayfish metarhodopsin as an intr...

Difference absorption spectra were recorded during the formation and decay of metarhodopsin III after sonicated membrane suspensions of rhodopsin were bleached at 37 degrees C. The data were analyzed using SVD, spectral decomposition and global exponential fitting. By comparison of the results in the presence or absence of 70 microM NADPH and those for bovine or human rhodopsin, a single compre...