Direct observation of the thermal equilibria among lumirhodopsin, metarhodopsin I, and metarhodopsin II in chicken rhodopsin

Imai, Hiroo; Mizukami, Taku; Imamoto, Yasushi; Shichida, Yoshinori

doi:10.1021/bi00251a049

Cited by 38 publications

(57 citation statements)

References 29 publications

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“…Such an equilibrium had been proposed earlier," but data supporting that proposal were originally not very extensive. Recent evidence from low-temperature studies of chicken rhodopsin 96 (see below) have directly observed such an equilibrium, so this feature seems to be on secure ground. Further work will be required to determine which of the possible mechanisms prevails, however, since with only three observed rates the problem remains underdetermined for the number of microscopic rates in the possible mechanisms.…”

Section: Current Picture Ofmeta II Formationmentioning

confidence: 84%

Spectral and Kinetic Characterization of Visual Pigment Photointermediates

Kliger

Lewis

1995

Israel Journal of Chemistry

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Abstract. The literature describing intermediates formed after photolysis of visualpigmentsis reviewed. Resultsobtainednear physiological temperatures using time-resolved optical density measurements in the UVNis region are emphasized. The general character of intermediates which appear in the course of protein function, and the role of methods with different time resolutions in their study, are discussed. Specificresults for intermediates from bathorhodopsin to metarhodopsin II are treated in detail, with limited discussion of the earlier and later species. The discussion centers on the best-understood pigment,bovine rhodopsin, but resultsfor cone-type and invertebrate pigments are also discussed. Comparison is made between the picture of the intermediates obtained using low-temperature trapping methodsand that obtainedusing kinetic measurements. The thermodynamic parameters of the intermediates are discussed, and their significance for the structure/ function of heptahelical protein intermediates in general is considered.

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Section: Current Picture Ofmeta II Formationmentioning

confidence: 84%

Spectral and Kinetic Characterization of Visual Pigment Photointermediates

Kliger

Lewis

1995

Israel Journal of Chemistry

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“…Then the spectra (curves 2 (dotted curve) in C and D) containing only meta-I and meta-II were calculated by subtracting the spectra of residual 11-cis-pigments and photo-regenerated 9-cis-pigments from the spectra recorded. The amounts of 11-cis-and 9-cis-pigments were estimated by simulation of the measured spectra at the wavelength regions longer than 580 nm (or 560 nm in E122Q sample) with those of 11-cis-and 9-cis-pigments (26,51). The amounts of 11-cis-and 9-cis-pigments present in the illuminated WT sample were 41.8 and 4.0%, respectively.…”

Section: Resultsmentioning

confidence: 99%

Molecular Properties of Rhodopsin and Rod Function

Imai

Kefalov

Sakurai

et al. 2007

Journal of Biological Chemistry

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Signal transduction in rod cells begins with photon absorption by rhodopsin and leads to the generation of an electrical response. The response profile is determined by the molecular properties of the phototransduction components. To examine how the molecular properties of rhodopsin correlate with the rod-response profile, we have generated a knock-in mouse with rhodopsin replaced by its E122Q mutant, which exhibits properties different from those of wild-type (WT) rhodopsin. Knock-in mouse rods with E122Q rhodopsin exhibited a photosensitivity about 70% of WT. Correspondingly, their single-photon response had an amplitude about 80% of WT, and a rate of decline from peak about 1.3 times of WT. The overall 30% lower photosensitivity of mutant rods can be explained by a lower pigment photosensitivity (0.9) and the smaller single-photon response (0.8). The slower decline of the response, however, did not correlate with the 10-fold shorter lifetime of the meta-II state of E122Q rhodopsin. This shorter lifetime became evident in the recovery phase of rod cells only when arrestin was absent. Simulation analysis of the photoresponse profile indicated that the slower decline and the smaller amplitude of the single-photon response can both be explained by the shift in the meta-I/ meta-II equilibrium of E122Q rhodopsin toward meta-I. The difference in meta-III lifetime between WT and E122Q mutant became obvious in the recovery phase of the dark current after moderate photobleaching of rod cells. Thus, the present study clearly reveals how the molecular properties of rhodopsin affect the amplitude, shape, and kinetics of the rod response.Light absorption by rhodopsin in rod photoreceptor cells results in the activation of a G protein-mediated signal transduction cascade that eventually generates an electrical response (1). The key proteins in this cascade have been identified, and their molecular properties as well as interactions with each other have been extensively investigated (2, 3). A current question is how well these properties and interactions correlate with the response profile of the photoreceptor cells. Although the gene knock-out approach has been very useful in addressing this question for the proteins rhodopsin kinase and arrestin (4, 5), this strategy is less appropriate for rhodopsin and G protein, because the deletions of these proteins eliminated the light response (6, 7). The gene knock-in approach is an alternative way, with a mutant protein replacing the wild-type (WT) 8 version. The maintenance of the same expression level of the protein in this procedure is important, because the interpretation can be difficult otherwise. For example, the photoresponse profile is altered when the rhodopsin content in rods is halved (8, 9).Our past work on comparing rhodopsin and cone pigments (10) has shown that their photosensitivities are not so different, but the meta-II (the G protein-activating state), as well as the subsequent meta-III, intermediates of cone pigments exhibit faster decay than those of rhodopsi...

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“…The pigment was regenerated by the addition of 2.5 nmol of 11-cis-retinal solubilized in ethanol (5 l) to each of opsin extracts (220 l of each). Then the pigment sample was subjected to low-temperature time-resolved spectroscopy to investigate formation and decay of meta II (29). The decay rate constants of meta II in native pigments were reported previously (11,15,30).…”

Section: Methodsmentioning

confidence: 99%

Single amino acid residue as a functional determinant of rod and cone visual pigments

Imai

Kojima

Oura

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

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139

141

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The visual transduction processes in rod and cone photoreceptor cells begin with photon absorption by the different types of visual pigments. Cone visual pigments exhibit faster regeneration from 11-cis-retinal and opsin and faster decay of physiologically active intermediate (meta II) than does the rod visual pigment, rhodopsin, as expected, due to the functional difference between rod and cone photoreceptor cells. To identify the amino acid residue(s) responsible for the difference in molecular properties between rod and cone visual pigments, we selected three amino acid positions (64, 122, and 150), where cone visual pigments have amino acid residues electrically different from those of rhodopsin, and prepared mutants of rhodopsin and chicken greensensitive cone visual pigment. The results showed that the replacement of Glu-122 of rhodopsin by the residue containing green-or red-sensitive cone pigment converted rhodopsin's rates of regeneration and meta II decay into those of the respective cone pigments, whereas the introduction of Glu-122 into green-sensitive cone visual pigment changed the rates of these processes into rates similar to those of rhodopsin. Furthermore, exchange of the residue at position 122 between rhodopsin and chicken green-sensitive cone pigment interchanges their efficiencies in activating retinal G protein transducin. Thus, the amino acid residue at position 122 is a functional determinant of rod and cone visual pigments.

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Direct observation of the thermal equilibria among lumirhodopsin, metarhodopsin I, and metarhodopsin II in chicken rhodopsin

Cited by 38 publications

References 29 publications

Spectral and Kinetic Characterization of Visual Pigment Photointermediates

Spectral and Kinetic Characterization of Visual Pigment Photointermediates

Molecular Properties of Rhodopsin and Rod Function

Single amino acid residue as a functional determinant of rod and cone visual pigments

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