1
|
Otsuka H, Mitsui H, Miura K, Okano K, Imamoto Y, Okano T. Rapid Oxidation Following Photoreduction in the Avian Cryptochrome4 Photocycle. Biochemistry 2020; 59:3615-3625. [PMID: 32915550 DOI: 10.1021/acs.biochem.0c00495] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Avian magnetoreception is assumed to occur in the retina. Although its molecular mechanism is unclear, magnetic field-dependent formation and the stability of radical-containing photointermediate(s) are suggested to play key roles in a hypothesis called the radical pair mechanism. Chicken cryptochrome4 (cCRY4) has been identified as a candidate magnetoreceptive molecule due to its expression in the retina and its ability to form stable flavin neutral radicals (FADH●) upon blue light absorption. Herein, we used millisecond flash photolysis to investigate the cCRY4 photocycle, in both the presence and absence of dithiothreitol (DTT); detecting the anion radical form of FAD (FAD●-) under both conditions. Using spectral data obtained during flash photolysis and UV-visible photospectroscopy, we estimated the absolute absorbance spectra of the photointermediates, thus allowing us to decompose each spectrum into its individual components. Notably, in the absence of DTT, approximately 37% and 63% of FAD●- was oxidized to FADOX and protonated to form FADH●, respectively. Singular value decomposition analysis suggested the presence of two FAD●- molecular species, each of which was destined to be oxidized to FADOX or protonated to FADH●. A tyrosine neutral radical was also detected; however, it likely decayed concomitantly with the oxidation of FAD●-. On the basis of these results, we considered the occurrence of bifurcation prior to FAD●- generation, or during FAD●- oxidization, and discussed the potential role played by the tyrosine radical in the radical pair mechanism.
Collapse
Affiliation(s)
- Hiroaki Otsuka
- Department of Electrical Engineering and Bioscience, Graduate School of Sciences and Engineering, Waseda University, TWIns, Wakamatsucho 2-2, Shinjuku-Ku, Tokyo 162-8480, Japan
| | - Hiromasa Mitsui
- Department of Electrical Engineering and Bioscience, Graduate School of Sciences and Engineering, Waseda University, TWIns, Wakamatsucho 2-2, Shinjuku-Ku, Tokyo 162-8480, Japan
| | - Kota Miura
- Department of Electrical Engineering and Bioscience, Graduate School of Sciences and Engineering, Waseda University, TWIns, Wakamatsucho 2-2, Shinjuku-Ku, Tokyo 162-8480, Japan
| | - Keiko Okano
- Department of Electrical Engineering and Bioscience, Graduate School of Sciences and Engineering, Waseda University, TWIns, Wakamatsucho 2-2, Shinjuku-Ku, Tokyo 162-8480, Japan
| | - Yasushi Imamoto
- Department of Biophysics, Division of Biological Sciences, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto 606-8502, Japan
| | - Toshiyuki Okano
- Department of Electrical Engineering and Bioscience, Graduate School of Sciences and Engineering, Waseda University, TWIns, Wakamatsucho 2-2, Shinjuku-Ku, Tokyo 162-8480, Japan
| |
Collapse
|
2
|
Shen YC, Sasaki T, Matsuyama T, Yamashita T, Shichida Y, Okitsu T, Yamano Y, Wada A, Ishizuka T, Yawo H, Imamoto Y. Red-Tuning of the Channelrhodopsin Spectrum Using Long Conjugated Retinal Analogues. Biochemistry 2018; 57:5544-5556. [DOI: 10.1021/acs.biochem.8b00583] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yi-Chung Shen
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Toshikazu Sasaki
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Take Matsuyama
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Takahiro Yamashita
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Yoshinori Shichida
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
- Research Organization of Science and Technology, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan
| | - Takashi Okitsu
- Laboratory of Organic Chemistry for Life Science, Kobe Pharmaceutical University, Kobe, Hyogo 658-0003, Japan
| | - Yumiko Yamano
- Laboratory of Organic Chemistry for Life Science, Kobe Pharmaceutical University, Kobe, Hyogo 658-0003, Japan
| | - Akimori Wada
- Laboratory of Organic Chemistry for Life Science, Kobe Pharmaceutical University, Kobe, Hyogo 658-0003, Japan
| | - Toru Ishizuka
- Department of Developmental Biology and Neuroscience, Graduate School of Life Science, Tohoku University, Sendai, Miyagi 980-8577, Japan
| | - Hiromu Yawo
- Department of Developmental Biology and Neuroscience, Graduate School of Life Science, Tohoku University, Sendai, Miyagi 980-8577, Japan
| | - Yasushi Imamoto
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| |
Collapse
|
3
|
Imamoto Y, Kojima K, Oka T, Maeda R, Shichida Y. Helical rearrangement of photoactivated rhodopsin in monomeric and dimeric forms probed by high-angle X-ray scattering. Photochem Photobiol Sci 2016; 14:1965-73. [PMID: 26293780 DOI: 10.1039/c5pp00175g] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Light-induced helical rearrangement of vertebrate visual rhodopsin was directly monitored by high-angle X-ray scattering (HAXS), ranging from Q (= 4π sin θ/λ) = 0.03 Å(-1) to Q = 1.5 Å(-1). HAXS of nanodiscs containing a single rhodopsin molecule was performed before and after photoactivation of rhodopsin. The intensity difference curve obtained by HAXS agreed with that calculated from the crystal structure of dark state rhodopsin and metarhodopsin II, indicating that the conformational change of monomeric rhodopsin in the membrane is consistent with that occurring in the crystal. On the other hand, the HAXS intensity difference curve of nanodiscs containing two rhodopsin molecules was significantly reduced, similar to that calculated from the crystal structure of the deprotonated intermediate, without a large conformational change. These results suggest that rhodopsin is dimerized in the membrane and that the interaction between rhodopsin molecules modulates structural changes.
Collapse
Affiliation(s)
- Yasushi Imamoto
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
| | - Keiichi Kojima
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
| | - Toshihiko Oka
- Department of Physics, Faculty of Science, Shizuoka University, Shizuoka 422-8529, Japan and Nanomaterials Research Division, Research Institute of Electronics, Shizuoka University, Shizuoka 432-8011, Japan
| | - Ryo Maeda
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
| | - Yoshinori Shichida
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
| |
Collapse
|
4
|
Kojima K, Imamoto Y, Maeda R, Yamashita T, Shichida Y. Rod visual pigment optimizes active state to achieve efficient G protein activation as compared with cone visual pigments. J Biol Chem 2013; 289:5061-73. [PMID: 24375403 DOI: 10.1074/jbc.m113.508507] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Most vertebrate retinas contain two types of photoreceptor cells, rods and cones, which show different photoresponses to mediate scotopic and photopic vision, respectively. These cells contain different types of visual pigments, rhodopsin and cone visual pigments, respectively, but little is known about the molecular properties of cone visual pigments under physiological conditions, making it difficult to link the molecular properties of rhodopsin and cone visual pigments with the differences in photoresponse between rods and cones. Here we prepared bovine and mouse rhodopsin (bvRh and mRh) and chicken and mouse green-sensitive cone visual pigments (cG and mG) embedded in nanodiscs and applied time-resolved fluorescence spectroscopy to compare their Gt activation efficiencies. Rhodopsin exhibited greater Gt activation efficiencies than cone visual pigments. Especially, the Gt activation efficiency of mRh was about 2.5-fold greater than that of mG at 37 °C, which is consistent with our previous electrophysiological data of knock-in mice. Although the active state (Meta-II) was in equilibrium with inactive states (Meta-I and Meta-III), quantitative determination of Meta-II in the equilibrium showed that the Gt activation efficiency per Meta-II of bvRh was also greater than those of cG and mG. These results indicated that efficient Gt activation by rhodopsin, resulting from an optimized active state of rhodopsin, is one of the causes of the high amplification efficiency of rods.
Collapse
Affiliation(s)
- Keiichi Kojima
- From the Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | | | | | | | | |
Collapse
|
5
|
Imamoto Y, Shichida Y. Cone visual pigments. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1837:664-73. [PMID: 24021171 DOI: 10.1016/j.bbabio.2013.08.009] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 08/07/2013] [Accepted: 08/30/2013] [Indexed: 12/16/2022]
Abstract
Cone visual pigments are visual opsins that are present in vertebrate cone photoreceptor cells and act as photoreceptor molecules responsible for photopic vision. Like the rod visual pigment rhodopsin, which is responsible for scotopic vision, cone visual pigments contain the chromophore 11-cis-retinal, which undergoes cis-trans isomerization resulting in the induction of conformational changes of the protein moiety to form a G protein-activating state. There are multiple types of cone visual pigments with different absorption maxima, which are the molecular basis of color discrimination in animals. Cone visual pigments form a phylogenetic sister group with non-visual opsin groups such as pinopsin, VA opsin, parapinopsin and parietopsin groups. Cone visual pigments diverged into four groups with different absorption maxima, and the rhodopsin group diverged from one of the four groups of cone visual pigments. The photochemical behavior of cone visual pigments is similar to that of pinopsin but considerably different from those of other non-visual opsins. G protein activation efficiency of cone visual pigments is also comparable to that of pinopsin but higher than that of the other non-visual opsins. Recent measurements with sufficient time-resolution demonstrated that G protein activation efficiency of cone visual pigments is lower than that of rhodopsin, which is one of the molecular bases for the lower amplification of cones compared to rods. In this review, the uniqueness of cone visual pigments is shown by comparison of their molecular properties with those of non-visual opsins and rhodopsin. This article is part of a Special Issue entitled: Retinal Proteins - You can teach an old dog new tricks.
Collapse
Affiliation(s)
- Yasushi Imamoto
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Yoshinori Shichida
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
| |
Collapse
|
6
|
Imamoto Y, Seki I, Yamashita T, Shichida Y. Efficiencies of activation of transducin by cone and rod visual pigments. Biochemistry 2013; 52:3010-8. [PMID: 23570417 DOI: 10.1021/bi3015967] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
How the light-induced transducin (Gt) activation process differs biochemically between cone visual pigments and rod visual pigment (rhodopsin) has remained unclear, because the Gt-activating state (Meta-II) of cone visual pigment decays too fast to precisely measure the activation efficiency by conventional biochemical methods such as the GTPγS binding assay. Here we measured the activation efficiencies of chicken green-sensitive cone visual pigment (cG) and bovine rhodopsin (bRh) in real time by monitoring the intrinsic fluorescence of tryptophan residues in the pigments and Gt. Michaelis-Menten analysis of Gt activation showed that the initial velocity for cG was approximately half that for bRh, while their Michaelis constants were comparable. Gt activation by cG was immediately slowed because of the fast hydrolysis of the retinal Schiff base in Meta-II, but this hydrolysis was suppressed by forming the complex with Gt. Using mutants of cG and bRh for positions 122 and 189, which exhibit altered rates of chromophore hydrolysis in Meta-II, we found that the initial velocity of Gt activation is negatively correlated with the rate of chromophore hydrolysis. These results suggest that the amino acid residues at positions 122 and 189 account for not only the resistance to the chromophore hydrolysis in Meta-II but also the conformation of Meta-II for efficient Gt activation. The substantially longer lifetime of the Gt activating state of Rh would be necessary to suppress the spontaneous quenching by the stochastic decay of the Gt-activating state when a rod responds to a single photon.
Collapse
Affiliation(s)
- Yasushi Imamoto
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | | | | | | |
Collapse
|
7
|
Sato K, Yamashita T, Imamoto Y, Shichida Y. Comparative Studies on the Late Bleaching Processes of Four Kinds of Cone Visual Pigments and Rod Visual Pigment. Biochemistry 2012; 51:4300-8. [DOI: 10.1021/bi3000885] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Keita Sato
- Department of Biophysics,
Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Takahiro Yamashita
- Department of Biophysics,
Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Yasushi Imamoto
- Department of Biophysics,
Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Yoshinori Shichida
- Department of Biophysics,
Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| |
Collapse
|
8
|
Mooney VL, Szundi I, Lewis JW, Yan ECY, Kliger DS. Schiff base protonation changes in Siberian hamster ultraviolet cone pigment photointermediates. Biochemistry 2012; 51:2630-7. [PMID: 22394396 DOI: 10.1021/bi300157r] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Molecular structure and function studies of vertebrate ultraviolet (UV) cone visual pigments are needed to understand the molecular evolution of these photoreceptors, which uniquely contain unprotonated Schiff base linkages between the 11-cis-retinal chromophore and the opsin proteins. In this study, the Siberian hamster ultraviolet cone pigment (SHUV) was expressed and purified in an n-dodecyl-β-D-maltoside suspension for optical characterization. Time-resolved absorbance measurements, over a spectral range from 300 to 700 nm, were taken for the purified pigment at time delays from 30 ns to 4.64 s after photoexcitation using 7 ns pulses of 355 nm light. The resulting data were fit globally to a sum of exponential functions after noise reduction using singular-value decomposition. Four exponentials best fit the data with lifetimes of 1.4 μs, 210 μs, 47 ms, and 1 s. The first photointermediate species characterized here is an equilibrated mixture similar to the one formed after rhodopsin's Batho intermediate decays into equilibrium with its successor, BSI. The extremely large red shift of the SHUV Batho component relative to the pigment suggests that SHUV Batho has a protonated Schiff base and that the SHUV cone pigment itself has an unprotonated Schiff base. In contrast to SHUV Batho, the portion of the equilibrated mixture's spectrum corresponding to SHUV BSI is well fit by a model spectrum with an unprotonated Schiff base. The spectra of the next two photointermediate species revealed that they both have unprotonated Schiff bases and suggest they are analogous to rhodopsin's Lumi I and Lumi II species. After decay of SHUV Lumi II, the correspondence with rhodopsin photointermediates breaks down and the next photointermediate, presumably including the G protein-activating species, is a mixture of protonated and unprotonated Schiff base photointermediate species.
Collapse
Affiliation(s)
- Victoria L Mooney
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | | | | | | | | |
Collapse
|
9
|
Mielcarek J, Grobelny P, Osmałek T. Identification of photoproducts of fluvastatin in solutions. JPC-J PLANAR CHROMAT 2009. [DOI: 10.1556/jpc.22.2009.2.11] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
10
|
Hisatomi O, Iwasa T, Kataoka M, Ebrey T. Introduction to the Symposium-in-Print on Photoreceptors and Signal Transduction in Honor of Professor Fumio Tokunaga. Photochem Photobiol 2008. [DOI: 10.1111/j.1751-1097.2008.00391.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|