Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Opsins”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21Linked to original sources
PubMed1989

Immunoelectron microscopical examination of the surface distribution of opsin in rat rod photoreceptor cells.

The distribution of the visual pigment protein opsin in postnatal day 8 and adult rat retinal photoreceptor cells was studied using several well characterized monoclonal antibodies against rhodopsin and a sensitive, modified colloidal gold technique. Distribution of opsin was studied in intact tissue, explant cultures and freshly dissociated cell preparation. At PN8 labeling was seen in the plasma membrane overlying the cell body, inner and outer segment. Adult retinas still showed heavy labeling of the cell body and outer segment, but reduced labeling of the inner segment surface. Semi-quantitative estimates of colloidal gold particles bound indicated a ratio of 3-20 times more particles per unit length in the outer vs. the inner segment, depending on tissue age, preparation and antibody. Together with the subcellular localization of other photoreceptor plasma membrane proteins, these data reveal a complex system of membrane domains into which different protein components are segregated.

Animals↗
PubMed1992

Maintenance of opsin and S-antigen gene expression in RCS dystrophic rats following RPE transplantation.

The effects of retinal pigment epithelium (RPE) transplantation in rescuing photoreceptor cells (PRC) were studied in RCS rats bearing the rdy mutation. RPE preparations from Long-Evans rats were transplanted into the subretinal space of post-natal (P) 17-19-day-old RCS rats. Age-matched RCS animals in the control group received injections of the transplantation vehicle buffer alone. The animals were killed at various post-natal ages after RPE transplantation. Immunocytochemical studies using antibodies to opsin and S-antigen indicated intact photoreceptor cells in the transplanted retinas. In contrast age-matched sham-injected animals did not show any rescue of photoreceptor cells at P90. Single RPE transplantation of 60,000 cells in each eye resulted in restoration of near normal mRNA levels for opsin, and S-antigen proteins. Comparisons of mRNA levels of two visual proteins using cDNA probes demonstrated a therapeutic effect of RPE transplantation in preventing a progressive decline in mRNA levels due to retinal degeneration. In contrast, P109 sham-injected controls showed no detectable mRNA levels for these proteins. In vitro protein synthesis in RPE-transplanted retinas implied further competence of these retinas. These data suggest that RPE transplantation not only rescues photoreceptors from degeneration, but more importantly, it allows normal transcription and translation in these cells rendering them capable of participating in the visual and signal transduction cascade.

Animals↗
PubMed1988

Acidic fibroblast growth factor stimulates opsin levels in retinal photoreceptor cells in vitro.

It is demonstrated that newborn rat retinal photoreceptor cells can differentiate in monolayer culture, and synthesize de novo photoreceptor-specific proteins such as opsin. When maintained in serum supplemented medium on a laminin substrate, these cells survive for up to 3 weeks. The addition of acidic fibroblast growth factor stimulates an increase in the levels of opsin of 5-10-fold control values, and prolongs cell survival by up to 6 days.

Animals↗
PubMed1995

Topographical regulation of cone and rod opsin genes: parallel, position dependent levels of transcription.

RNase protection assays were used to follow rhodopsin and red cone opsin mRNA levels during bovine fetal development as a function of retinal position. Following induction, an equivalent radial gradient of rod and cone opsin mRNA is present in the fetal retina. This gradient is maintained in the adult retina even though no corresponding gradient in rod or cone cell density is present. Since the mRNA expression gradient does not progress radially, position dependent levels of photoreceptor-specific transcription is suggested.

Animals↗
PubMed2006

Exon-skipping variant of RGR opsin in human retina and pigment epithelium.

An extraneous exon-skipping mRNA encodes an altered form of a light-absorbing opsin in human retina and pigment epithelium (RPE). The predicted protein variant differs from full-length RPE-retinal G protein-coupled receptor (RGR) by having an in-frame deletion of exon 6, which contains the entire sixth transmembrane domain. To verify that the exon 6-deleted RGR protein (RGR-d) exists in human retinas, we have produced RGR-d antibody probes. In Western blot assays, the RGR-d protein was detected in retinas of a large proportion ( approximately 53%) of individual donors, including patients with age-related macular degeneration (AMD). The relative abundance of RGR-d varied significantly between individuals. The altered protein is expressed in RPE cells and has a more basal subcellular localization that is remarkably different from that of normal RGR opsin. The presence of this exon-skipping variant of RGR in humans may contribute to the progressive derangement of the RPE.

Aged↗
PubMed2005

Convergent loss of an anciently duplicated, functionally divergent RH2 opsin gene in the fugu and Tetraodon pufferfish lineages.

We describe the complete opsin gene families from the sequenced fugu and Tetraodon pufferfish genomes. We report the convergent loss of function of an anciently duplicated, functionally divergent RH2 or "green-sensitive" opsin gene in both pufferfish lineages, designated RH2-2. In fugu, RH2-2 apparently ceased to function very recently following a transposon-induced deletion that truncated the N-terminal 115 amino acids from the translated protein. Although a lack of frameshift or nonsense mutations in the fugu RH2-2 pseudogene suggests that the gene was lost very recently in this lineage, we were unable to detect any evidence of a selective sweep associated with the fixation of the truncated allele from population data. Interspecific comparison of the remaining fugu RH2-2 coding sequence paradoxically indicates that the gene was under strong purifying selection until the truncation occurred.

Amino Acid Sequence↗
PubMed2005

DISCO! Dissociation of cone opsins: the fast and noisy life of cones explained.

Vertebrate retinas contain two types of photoreceptors. Rods are for vision in dim light, while cones provide high-speed color vision in bright light. In this issue of Neuron, Kefalov et al. present data to explain the reduced sensitivity and faster response kinetics of cones. They show that the chromophore dissociates from cone but not rod visual pigment, yielding apo-opsin. This apo-opsin activates the signaling cascade to desensitize cones and speed the photoresponse.

Ambystoma↗
PubMed2002

Variations in long- and middle-wavelength-sensitive opsin gene loci in crab-eating monkeys.

We analyzed variations in long (L)- and middle (M)-wavelength-sensitive opsin gene loci in crab-eating monkeys. Unlike humans, most monkeys have a single L and a single M gene. Two variant genotypes, one with only one opsin gene (dichromatic) and one with tandemly arrayed multiple genes, were also found in the monkeys. However, the frequency of the former was 0.47%, and that of the latter was 5% in the monkeys, while 2% and 66%, respectively, in Caucasian males. The two variants were found only in Java Island, Indonesia, and South Thailand, respectively. The data suggest that the frequency of each genotype is different among Old World primates.

Animals↗
PubMed1999

Visual pigments and oil droplets in the retina of a passerine bird, the canary Serinus canaria: microspectrophotometry and opsin sequences.

The visual receptors of the passeriform bird Serinus canaria, the canary, have been examined microspectrophotometrically and the sequences of the opsins determined. Rods have a maximum absorbance (lambda max) at 506 nm. Four spectral classes of single cone are present: long-wave-sensitive (LWS) containing a photopigment with lambda max at 569 nm, middle-wave-sensitive (MWS) with lambda max at 505 nm, short-wave-sensitive (SWS) with lambda max at 442 nm, and ultraviolet-sensitive (UVS) with lambda max at about 366 nm. Double cones possess the 569-nm pigment in both members. Typical combinations of photopigment and oil droplet occur in most cone classes. An ambiguity exists in the oil droplet of the single LWS cones. In some birds, LWS cones are paired with an R-type droplet, whereas in the majority of canaries the LWS pigment is paired with a droplet similar to the P-type of double cones. Mechanisms of spectral tuning within each opsin class are discussed.

Animals↗
PubMed2002

Xenopus laevis red cone opsin and Prph2 promoters allow transgene expression in amphibian cones, or both rods and cones.

We have cloned the promoter regions of two Xenopus laevis genes, Prph2 (also called RDS) and red cone opsin (RCO) using a polymerase chain reaction-based gene-walking method. The proteins coded by these genes are expressed exclusively in retinal photoreceptors. Although these promoter sequences are evolutionarily distant from previously described homologues, potentially informative similarities were noted that suggest conserved binding sites of the transcription factors Crx and Rx. The promoters were tested for function in transgenic X. laevis. RCO-driven expression was restricted to cones and pinealocytes, while the Prph2 promoter drove expression of a reporter green fluorescent protein transgene in both rod and cone photoreceptors, as well as low levels of expression in muscle tissue. This is the first description of transgene expression driven by a Prph2 promoter homologue from any species. In combination with the previously reported X. laevis opsin and arrestin promoters, these sequences will facilitate the development and analysis of X. laevis models of inherited retinal degeneration.

Animals↗
PubMed1999

Opsin shift in an aldolase antibody.

An antibody-retinal assembly that mimics the opsin shift (OS) of the naturally occurring visual pigments is reported. Both experiments and calculations show that the aldolase antibody 33F12 covalently binds all-trans retinal via a protonated Schiff base with a lysine residue. This chromophore, which exhibits a remarkable opsin red shift (140 nm), represents a useful model system for studying the factors that contribute to the OS.

Antibodies↗
PubMedDate not supplied

Temporal and spatial patterns of opsin gene expression in zebrafish (Danio rerio).

In zebrafish, the first class of cone photoreceptor to become morphologically distinct is the ultraviolet-sensitive short single cone, at 4 days postfertilization, whereas the last class, the red- and green-sensitive double cone, becomes distinct at 10 days postfertilization. We have examined the time course of visual pigment gene expression in zebrafish using whole-mount in situ hybridization. Within the retina, opsins may be detected as early as 40 h postfertilization with the ultraviolet and rod visual pigments being expressed before the blue- (48 h) and red- (60 h) sensitive pigments. In the pineal, red-sensitive opsin is expressed at 48 h postfertilization. Visual pigment expression provides a useful tool for investigations of early cell fate in zebrafish.

Animals↗
PubMedDate not supplied

Cone and rod inputs to murine retinal ganglion cells: evidence of cone opsin specific channels.

To identify ultraviolet (UV) and middle- (M) wavelength-sensitive cone and rod signals in murine retinal ganglion cells, single ganglion cell responses were studied in anesthetized, light-adapted C57/BL6 mice with tungsten microelectrodes driven through the sclera and vitreous to the neural retina. One hundred fifty-four ganglion cells were examined in 43 retinas of 34 mice. The retina was stimulated with diffuse flashes and/or pulses of ultraviolet (360 nm) or green (520 nm) light in the presence and absence of a strong steady orange adapting light. Twelve ganglion cells were studied in the dark-adapted retina in order to identify the signals of rods. Three functionally different types of ganglion cells were found: (1) phasic responding cells (31%) with no spontaneous activity and large impulse amplitudes; (2) tonic responding cells (60%) with irregular, low frequency (5-10 Hz) spontaneous activity and smaller impulse amplitudes; and (3) metronome-like cells (9%) with regular, relatively high-frequency (20-40 Hz) spontaneous activity. A few cells (1%) had habituating responses. Every cell encountered was affected by diffuse stimulation. The more common two types were excited at either the ON or OFF or at both the ON and OFF phases of stimulation. Type III cells had weaker responses, sometimes only inhibited by turning off a light. In the light-adapted state, most cells received signals of the same polarity from UV- and M-cones but UV-cone inputs were usually more dominant, especially in ventral retina. A fraction of cells received signals from only UV- (18%) or only M- (3%) cones. In rare cases (2%) these cone inputs had an opposite polarity on the same cell. In the dark-adapted state, all cells were at least four or five logarithmic units more sensitive and more to green than ultraviolet light. The results indicate that co-expression of both UV-and M-cone opsins cannot be ubiquitous in murine retina. Some cones, especially UV cones, exist without the presence of any functional M-cone opsin. This must be the case to explain the presence of ganglion cells that receive inputs only from UV-cones and others that receive inputs of opposite polarity from UV- and M-cones. The results support the hypothesis that murine retina has the physiological capacity to relay signals to the brain that allow the sensing of chromatic contrast and color vision.

Adaptation, Physiological↗
PubMed1994

A human opsin-related gene that encodes a retinaldehyde-binding protein.

The ligand-binding property of a cytoplasmic membrane-bound protein from bovine retinal pigment epithelium (RPE) has been demonstrated. The putative RPE-retinal G protein coupled receptor (RGR) covalently binds both all-trans- and 11-cis-retinal after reduction by sodium borohydride. The 32-kDa receptor binds all-trans-retinal preferentially, rather than the 11-cis isomer. The amino acid sequence of the opsin-related protein in humans is 86% identical to that of bovine RGR, and a lysine residue, analogous to the retinaldehyde attachment site of rhodopsin, is conserved in the seventh transmembrane domain of RGR in both species. The human gene that encodes the novel retinaldehyde receptor spans 14.8 kb and is split into seven exons. The structure of the gene is distinct from that of the visual pigment genes. These findings support the notion that the rgr gene represents the earliest independent branch of the vertebrate opsin gene family. A second form of human RGR in retina is predicted by alternative splicing of its precursor mRNA. This RGR variant results from the alternative use of an internal acceptor splice site in the second intron of the human gene, and it contains an insertion of four amino acids in the connecting loop between the second and thrid transmembrane domains. Since RGR binds all-trans-retinal preferentially, one of its functions may be to catalyze isomerization of the chromophore by a retinochrome-like mechanism.

Amino Acid Sequence↗
PubMed1980

Aromatic retinal analogues and their interaction with cattle opsin.

The preparation of seven aromatic analogues of retinal, the isolation and characterization of their geometric isomers, and the interaction of these isomers with cattle opsin are reported. Within certain limitations, it has been demonstrated that stable aromatic rhodopsin analogues can be prepared. In general, the stereoselectivity of isomers of these compounds in their interaction with opsin and the absorption properties of the resultant pigments are similar to those of the parent retinal.

Animals↗
PubMed2001

Thermal destabilization of rhodopsin and opsin by proteolytic cleavage in bovine rod outer segment disk membranes.

The G-protein coupled receptor, rhodopsin, consists of seven transmembrane helices which are buried in the lipid bilayer and are connected by loop domains extending out of the hydrophobic core. The thermal stability of rhodopsin and its bleached form, opsin, was investigated using differential scanning calorimetry (DSC). The thermal transitions were asymmetric, and the temperatures of the thermal transitions were scan rate dependent. This dependence exhibited characteristics of a two-state irreversible denaturation in which intermediate states rapidly proceed to the final irreversible state. These studies suggest that the denaturation of both rhodopsin and opsin is kinetically controlled. The denaturation of the intact protein was compared to three proteolytically cleaved forms of the protein. Trypsin removed nine residues of the carboxyl terminus, papain removed 28 residues of the carboxyl terminus and a portion of the third cytoplasmic loop, and chymotrypsin cleaved cytoplasmic loops 2 and 3. In each of these cases the fragments remained associated as a complex in the membrane. DSC studies were carried out on each of the fragmented proteins. In all of the samples the scan rate dependence of the Tm indicated that the transition was kinetically controlled. Trypsin-proteolyzed protein differed little from the intact protein. However, the activation energy for denaturation was decreased when cytoplasmic loop 3 was cleaved by papain or chymotrypsin. This was observed for both bleached and unbleached samples. In the presence of the chromophore, 11-cis-retinal, the noncovalent interactions among the proteolytic fragments produced by papain and chymotrypsin cleavage were sufficiently strong such that each of the complexes denatured as a unit. Upon bleaching, the papain fragments exhibited a single thermal transition. However, after bleaching, the chymotrypsin fragments exhibited two calorimetric transitions. These data suggest that the loops of rhodopsin exert a stabilizing effect on the protein.

Amino Acid Sequence↗
PubMed1996

Blue and ultraviolet light-absorbing opsin from the retinal pigment epithelium.

The retinal pigment epithelium (RPE) contains an abundant opsin that is distinct from rhodopsin and cone visual pigments and is able to bind the retinaldehyde chromophore. The putative retinal G protein-coupled receptor (RGR) was isolated in digitonin solution from bovine RPE microsomes and copurified consistently with a minor 34-kDa protein. The absorption spectrum of RGR revealed endogenous pH-sensitive absorbance in the blue and near-ultraviolet regions of light. Membrane-bound RGR was incubated with exogenously added all-trans-retinal and formed two long-lived pH-dependent photopigments with absorption maxima of 469 +/- 2.4 and 370 +/- 7.3 nm. The effects of hydrogen ion concentration suggest that the blue and near-UV photopigments are tautomeric forms of RGR, in which an all-trans-retinal Schiff base is protonated or unprotonated, respectively. The RPE pigment was also demonstrable by its reactivity to hydroxylamine in the dark. The retinaldehyde-RGR conjugate at neutral pH favors the near-UV pigment and is a novel light-absorbing opsin in the vertebrate eye.

Animals↗
PubMedDate not supplied

Bovine opsin has more than one signal sequence.

By deletion of selected segments from a bovine opsin complementary DNA clone and subsequent analysis of transcripts in a cell-free translation-translocation system, we have localized two out of four theoretically conceivable signal sequences required for the integration of opsin into microsomal membranes.

Amino Acid Sequence↗