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Donat-P Häder, Mineo Iseki
Motile microorganisms such as the green Euglena gracilis use a number of external stimuli to orient in their environment. They respond to light with photophobic responses, photokinesis and phototaxis, all of which can result in accumulations of the organisms in suitable habitats. The light responses operate synergistically with gravitaxis, aerotaxis and other responses. Originally the microscopically obvious stigma was thought to be the photoreceptor, but later the paraxonemal body (PAB, paraflagellar body) has been identified as the light responsive organelle, located in the trailing flagellum inside the reservoir...
2017: Advances in Experimental Medicine and Biology
Kousuke Kajimoto, Takashi Kikukawa, Hiroki Nakashima, Haruki Yamaryo, Yuta Saito, Tomotsumi Fujisawa, Makoto Demura, Masashi Unno
Sodium-ion-pump rhodopsin (NaR) is a microbial rhodopsin that transports Na(+) during its photocycle. Here we explore the photocycle mechanism of NaR from Indibacter alkaliphilus with transient absorption and transient resonance Raman spectroscopy. The transient absorption data indicate that the photocycle of NaR is K (545 nm) → L (490 nm)/M (420 nm) → O1 (590 nm) → O2 (560 nm) → NaR, where the L and M are formed as equilibrium states. The presence of K, L, M, and O intermediates was confirmed by the resonance Raman spectra with 442 and 532 nm excitation...
April 21, 2017: Journal of Physical Chemistry. B
Joydip Kundu, Andrew Michaelson, Petr Baranov, Marco Chiumiento, Tom Nigl, Michael J Young, Rebecca L Carrier
While cell transplantation therapies show great promise as treatments for retinal degeneration, the challenge of low cell survival upon transplantation motivates exploration of materials that may serve as cell delivery vehicles and promote survival and differentiation. In this study, we explored the native matrix that surrounds the outer segments of photoreceptors and promotes their homeostasis, interphotoreceptor matrix (IPM), as a substrate for human retinal progenitor cells (hRPCs). Bovine IPM was characterized to determine its structure and biochemical composition, and processed to develop substrates for cells...
April 18, 2017: Journal of Biomedical Materials Research. Part B, Applied Biomaterials
Serena Buscone, Andrei N Mardaryev, Bianca Raafs, Jan W Bikker, Carsten Sticht, Norbert Gretz, Nilofer Farjo, Natallia E Uzunbajakava, Natalia V Botchkareva
BACKGROUND AND OBJECTIVE: Though devices for hair growth based on low levels of light have shown encouraging results, further improvements of their efficacy is impeded by a lack of knowledge on the exact molecular targets that mediate physiological response in skin and hair follicle. The aim of this study was to investigate the expression of selected light-sensitive receptors in the human hair follicle and to study the impact of UV-free blue light on hair growth ex vivo. MATERIAL AND METHODS: The expression of Opsin receptors in human skin and hair follicles has been characterized using RT-qPCR and immunofluorescence approaches...
April 18, 2017: Lasers in Surgery and Medicine
Alemeh Zamani, Shigeo Sakuragi, Toru Ishizuka, Hiromu Yawo
Channelrhodopsin (ChR)-1 and ChR2 were the first-identified members of ChRs which are a growing subfamily of microbial-type rhodopsins. Light absorption drives the generation of a photocurrent in cell membranes expressing ChR2. However, the photocurrent amplitude attenuates and becomes steady-state during prolonged irradiation. This process, called desensitization or inactivation, has been attributed to the accumulation of intermediates less conductive to cations. Here we provided evidence that the dark-adapted (DA) photocurrent before desensitization is kinetically different from the light-adapted (LA) one after desensitization, that is, the deceleration of both basal-to-conductive and conductive-to-basal transitions...
2017: Biophysics and Physicobiology
Lukas Hofmann, Nathan S Alexander, Wenyu Sun, Jianye Zhang, Tivadar Orban, Krzysztof Palczewski
Opsins comprise the protein component of light sensitive G protein-coupled receptors (GPCRs) in the retina of the eye that are responsible for the transduction of light into a biochemical signal. Here, we used hydrogen/deuterium (H/D) exchange coupled with mass spectrometry to map conformational changes in green cone opsin upon light activation. We then compared these findings with those reported for rhodopsin. The extent of H/D exchange in green cone opsin was greater than in rhodopsin in the dark and bleached states, suggesting a higher structural heterogeneity for green cone opsin...
April 21, 2017: Biochemistry
Lars Wöhlbrand, Bernd Wemheuer, Christoph Feenders, Hanna S Ruppersberg, Christina Hinrichs, Bernd Blasius, Rolf Daniel, Ralf Rabus
Annually recurring phytoplankton spring blooms are characteristic of temperate coastal shelf seas. During these blooms, environmental conditions, including nutrient availability, differ considerably from non-bloom conditions, affecting the entire ecosystem including the bacterioplankton. Accordingly, the emerging ecological niches during bloom transition are occupied by different bacterial populations, with Roseobacter RCA cluster and SAR92 clade members exhibiting high metabolic activity during bloom events...
2017: Frontiers in Microbiology
Eva Rabing Brix Petersen, Dorte Aalund Olsen, Henry Christensen, Søren Berndt Hansen, Cramer Christensen, Ivan Brandslund
BACKGROUND: Diabetic retinopathy (DR) is the most frequent cause of blindness among younger adults in the western world. No blood biomarkers exist to detect DR. Hypothetically, Rhodopsin concentrations in blood has been suggested as an early marker for retinal damage. The aim of this study was therefore to develop and validate a Rhodopsin assay by employing digital ELISA technology, and to investigate whether Rhodopsin concentrations in diabetes patients with DR are elevated compared with diabetes patients without DR...
April 5, 2017: Journal of Immunological Methods
Nojood A Altwaijry, Michael Baron, David W Wright, Peter Vivian Coveney, Andrea Townsend-Nicholson
The accurate identification of the specific points of interaction between G protein-coupled receptor (GPCR) oligomers is essential for the design of receptor ligands targeting oligomeric receptor targets. A coarse-grained molecular dynamics computer simulation approach would provide a compelling means of identifying these specific protein-protein interactions and could be applied both for known oligomers of interest and as a high-throughput screen to identify novel oligomeric targets. However, to be effective, this in silico modeling must provide accurate, precise, and reproducible information...
April 6, 2017: Journal of Chemical Theory and Computation
Shota Ito, Shinya Sugita, Keiichi Inoue, Hideki Kandori
Parvularcula oceani xenorhodopsin (PoXeR) is a light-driven inward proton pump that was discovered from deep ocean marine bacteria. PoXeR is categorized into the same family of Anabaena sensory rhodopsin (ASR) that functions as a photochromic sensor. In this paper, we applied light-induced difference Fourier-transform infrared (FTIR) spectroscopy to PoXeR at 77 K, and the obtained spectra were compared with those of ASR. The structure and structural changes in the primary processes of PoXeR are common to all microbial rhodopsins...
April 5, 2017: Photochemistry and Photobiology
Tian Wang, Stephen H Tsang, Jeannie Chen
Cyclic-GMP is a second messenger in phototransduction, a G-protein signaling cascade that conveys photon absorption by rhodopsin to a change in current at the rod photoreceptor outer segment plasma membrane. Basal cGMP level is strictly controlled by the opposing actions of phosphodiesterase (PDE6) and retinal guanylyl cyclases (GCs), and mutations in genes that disrupt cGMP homeostasis leads to retinal degeneration in humans through mechanisms that are incompletely understood. The purpose of this study is to examine two distinct cellular targets of cGMP: the cGMP-gated (CNG) channels and protein kinase G (PRKG), and how each may contribute to rod cell death...
April 3, 2017: Human Molecular Genetics
Zhaojing Lu, Xuebin Hu, Fei Liu, Dinesh C Soares, Xiliang Liu, Shanshan Yu, Meng Gao, Shanshan Han, Yayun Qin, Chang Li, Tao Jiang, Daji Luo, An-Yuan Guo, Zhaohui Tang, Mugen Liu
Mutations in EYS are associated with autosomal recessive retinitis pigmentosa (arRP) and autosomal recessive cone-rod dystrophy (arCRD) however, the function of EYS and the molecular mechanisms of how these mutations cause retinal degeneration are still unclear. Because EYS is absent in mouse and rat, and the structure of the retina differs substantially between humans and Drosophila, we utilised zebrafish as a model organism to study the function of EYS in the retina. We constructed an EYS-knockout zebrafish-line by TALEN technology which showed visual impairment at an early age, while the histological and immunofluorescence assays indicated the presence of progressive retinal degeneration with a cone predominately affected pattern...
April 5, 2017: Scientific Reports
Matteo Pappalardo, Mahmoud Rayan, Saleh Abu-Lafi, Martha E Leonardi, Danilo Milardi, Salvatore Guccione, Anwar Rayan
Modeling G-Protein Coupled Receptors (GPCRs) is an emergent field of research, since utility of high-quality models in receptor structure-based strategies might facilitate the discovery of interesting drug candidates. The findings from a quantitative analysis of eighteen resolved structures of rhodopsin family "A" receptors crystallized with antagonists and 153 pairs of structures are described. A strategy termed endeca-amino acids fragmentation was used to analyze the structures models aiming to detect the relationship between sequence identity and Root Mean Square Deviation (RMSD) at each trans-membrane-domain...
April 4, 2017: Molecular Informatics
Ned Van Eps, Lydia N Caro, Takefumi Morizumi, Ana Karin Kusnetzow, Michal Szczepek, Klaus Peter Hofmann, Timothy H Bayburt, Stephen G Sligar, Oliver P Ernst, Wayne L Hubbell
Conformational equilibria of G-protein-coupled receptors (GPCRs) are intimately involved in intracellular signaling. Here conformational substates of the GPCR rhodopsin are investigated in micelles of dodecyl maltoside (DDM) and in phospholipid nanodiscs by monitoring the spatial positions of transmembrane helices 6 and 7 at the cytoplasmic surface using site-directed spin labeling and double electron-electron resonance spectroscopy. The photoactivated receptor in DDM is dominated by one conformation with weak pH dependence...
April 3, 2017: Proceedings of the National Academy of Sciences of the United States of America
Stefan Sulmann, Amanda Kussrow, Darryl J Bornhop, Karl-Wilhelm Koch
Quantification of protein binding to membrane proteins is challenging and a limited set of methods is available to study such systems. Here we employed backscattering interferometry (BSI), a free-solution label-free method with high sensitivity, to quantify the interaction of neuronal Ca(2+)-Sensor proteins with their targets operating in phototransduction. We tested direct binding of guanylate cyclase-activating proteins (GCAP1 and GCAP2) to their membrane target guanylate cyclase 1. The regulatory mechanism of GCAPs including their binding interface in the target is unresolved...
March 31, 2017: Scientific Reports
Philip J M Johnson, Marwa H Farag, Alexei Halpin, Takefumi Morizumi, Valentyn I Prokhorenko, Jasper Knoester, Thomas L C Jansen, Oliver P Ernst, R J Dwayne Miller
Ultrafast photochemical reactions are initiated by vibronic transitions from the reactant ground state to the excited potential energy surface, directly populating excited-state vibrational modes. The primary photochemical reaction of vision, the isomerization of retinal in the protein rhodopsin, is known to be a vibrationally coherent reaction, but the Franck-Condon factors responsible for initiating the process have been difficult to resolve with conventional time-resolved spectroscopies. Here we employ experimental and theoretical 2D photon echo spectroscopy to directly resolve for the first time the Franck-Condon factors that initiate isomerization on the excited potential energy surface and track the reaction dynamics...
April 13, 2017: Journal of Physical Chemistry. B
Yanting Yin, Parker de Waal, Yuanzheng He, Li-Hua Zhao, Dehua Yang, Xiaoqing Cai, Yi Jiang, Karsten Melcher, Ming-Wei Wang, H Eric Xu
The glucagon receptor (GCGR) belongs to the secretin-like (class B) family of G protein-coupled receptors (GPCRs) and is activated by the peptide hormone, glucagon. The structures of an activated class B GPCR have remained unsolved, preventing a mechanistic understanding of how these receptors are activated. Using a combination of structural modeling and mutagenesis studies, we present here two modes of ligand-independent activation of GCGR. First, we identified a GCGR-specific hydrophobic lock comprising M338 and F345 within the IC3 loop and transmembrane helix 6 (TM6) and found that this lock stabilizes the TM6 helix in the inactive conformation...
March 29, 2017: Journal of Biological Chemistry
Benjamin S Krause, Christiane Grimm, Joel C D Kaufmann, Franziska Schneider, Thomas P Sakmar, Franz J Bartl, Peter Hegemann
Channelrhodopsins (ChRs) are light-activated ion channels widely employed for photostimulation of excitable cells. This study focuses on ReaChR, a chimeric ChR variant with optimal properties for optogenetic applications. We combined electrophysiological recordings with infrared and UV-visible spectroscopic measurements to investigate photocurrents and photochemical properties of ReaChR. Our data imply that ReaChR is green-light activated (λmax = 532 nm) with a non-rhodopsin-like action spectrum peaking at 610 nm for stationary photocurrents...
March 28, 2017: Biophysical Journal
Mostafa Soleimannejad, Somayeh Ebrahimi-Barough, Samad Nadri, Mohammad Riazi-Esfahani, Masoud Soleimani, Seyed Mohammad Tavangar, Jafar Ai
BACKGROUND: Retinitis pigmentosa (RP) and age related macular degeneration (AMD) are two retinal diseases that progress by photoreceptor cells death. In retinal transplantation studies, stem and progenitor cells inject into the sub retinal space or vitreous and then these cells can be migrate to the site of retinal degeneration and locate in the host retina and restitute vision. PRESENTATION OF THE HYPOTHESIS: Our hypothesis suggests that using human conjunctiva stem cells (as the source for increasing the number of human stem cells progenitor cells in retina dysfunction diseases) with fibrin gel and also assessing its relating in vitro (cellular and molecular processes) and in vivo (vision tests and pathology) could be a promising strategy for treatment of AMD and RP disorders...
April 2017: Medical Hypotheses
Adrian Yi, Hai Li, Natalia V Mamaeva, Roberto F de Cordoba, Johan Lugtenburg, Willem J DeGrip, John L Spudich, Kenneth J Rothschild
A recently discovered natural family of light-gated anion channelrhodopsins (ACRs) from cryptophyte algae provides an effective means of optogenetically silencing neurons. The most extensively studied ACR is from Guillardia theta (GtACR1). Earlier studies of GtACR1 have established a correlation between formation of a blue-shifted L-like intermediate and the anion channel "open" state. To study structural changes of GtACR1 in the K and L intermediates of the photocycle, a combination of low-temperature FTIR and UV-visible absorption difference spectroscopy was used along with stable-isotope retinal labeling and site-directed mutagenesis...
March 28, 2017: Biochemistry
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