Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Transducin”

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 775 records · Page 43Linked to original sources
PubMed2005

A hypothesis for GPCR activation.

Growing evidence that rhodopsin (RD) and related G protein-coupled receptors form functional dimers/oligomers, followed by direct proof (using atomic force microscopy) that in the retina disc membrane RD associates into a paracrystalline network of rows of dimers, need models of the RD-transducin (Gt) complex that would envision an optimal RD dimer/oligomer able to satisfy all well-documented interactions with Gt. Of the models proposed so far, only a few refer to RD dimers and only one of them proposes a complex of Gt with an RD oligomer (Filipek S, Krzyśko KA, Fotiadis D, Liang Y, Saperstein DA, Engel, A, Palczewski K Photochem Photobiol Sci 3: 628-638, 2004). This paper puts forward a hypothesis on another arrangement of RD monomers into the reported network of rows of dimers. Arguments for the compatibility of this set-up with interactions and activation of RD in the complex with Gt, in particular, with the well-documented movement of transmembrane helix 6 and cytosolic loop 3, which is vital for RD activation, are provided and discussed.

Dimerization↗
PubMed2005

Molecular analysis of TBL1Y, a Y-linked homologue of TBL1X related with X-linked late-onset sensorineural deafness.

Recent progress in sequencing the human Y chromosome has unveiled a series of X-Y homologous genes. In the present study, we focused on Transducin beta-like 1Y (TBL1Y), which is a Y-linked homologue of TBL1X that is related with X-linked late-onset sensorineural deafness. Recently, it has been shown that TBLR1, another homologue whose gene resides on chromosome 3, and TBL1X act as a corepressor/coactivator exchanger for several nuclear receptors and transcription factors. However, the expression pattern and function of TBL1Y remain unknown. The RT-PCR analysis of the TBL1 family revealed that TBL1Y was expressed in all 13 tissues examined but not in leukocytes. Among the cell lines tested, however, it was only expressed in NT2/D1 cells and in lymphoblasts transformed with Epstein Barr (EB) virus. To compare the functions of the TBL1 family, we generated a series of expression plasmids for GAL4DBD-fused proteins of the TBL1 family. We carried out dual luciferase assays using these plasmids in combination with a plasmid having a luciferase reporter gene harboring 5xGAL4 binding sites. Unlike the other constructs, GAL4DBD-fused TBL1Y did not repress the promoter activity. Moreover, we found three novel polymorphisms in the TBL1Y gene, IVS7+9G>A, G268C, and IVS7+1G>C, which is presumed to cause splicing error. These polymorphisms are found in males within Y-haplogroup O3 (XO3e), which is defined as the Y-haplogroup O3 excluding O3e, a branch of O3. The results show that TBL1Y differs from other members of the TBL1 family in expression and function, suggesting other roles in maleness.

Age of Onset↗
PubMed1992

Phosphatidic acid and polyphosphoinositide metabolism in rod outer segments. Differential role of soluble and peripheral proteins.

The phosphorylation of endogenous diacylglycerol (DAG) and phosphoinositides by [tau-32P]ATP was studied in bovine rod outer segments (ROS) selectively depleted of soluble or peripheral and soluble proteins by treatment with moderate (100 mM) or low (5 mM) ionic strength medium, respectively. DAG kinase activity was similar in bleached and non-bleached ROS extracted with 100 mM medium, and amounted to 70% of that observed in the corresponding non-extracted ROS. Phosphatidic acid (PtdH) labelling in ROS extracted in the dark with low ionic strength medium was markedly lower than in those extracted in light. Thus, even when a major proportion of DAG kinase was associated to the membrane, a soluble form also occurred. Most of the membrane-bound fraction behaved as a peripherally associated protein, its binding to the membrane being modified by light. Ir ROS extracted at moderate ionic strength the labelling of inositides was similar to that in non-extracted ROS. A marked enhancement in polyphosphoinositide labelling was observed in ROS extracted in the dark with low ionic strength. Alkaline treatment of ROS also produced inhibition of polyphosphoinositide phosphorylation. A peripheral form of a type C phospholipase, or a peripheral protein-mediated activation of a particulate form thereof, is suggested. Labelled polyphosphoinositides were more actively hydrolyzed in the light and in the dark plus GTP tau S than in the dark-incubated membranes. The results of phosphorylation experiments in membranes where differential extraction of the alpha subunit of transducin was carried out suggest that alpha and beta tau subunits may play opposite modulating roles in PtdH and polyphosphoinositide metabolism.

Animals↗
PubMed1985

Antisera to synthetic peptides of bovine rhodopsin: use as site-specific probes of disc membrane changes in retinal dystrophic dogs.

Based on the amino acid sequence of bovine rhodopsin, five peptides corresponding to the carboxyl terminus and one loop region have been synthesized. Rabbit antisera to these peptides recognize rhodopsin in whole bovine and dog retinas. Antisera were used to detect differences in specific regions of rhodopsin in dystrophic vs normal dog retinas. As detected on both "dot blots" and Western blots, rhodopsin from retinas of dystrophic dogs has a reduced reaction with antisera to peptides, Rhod-4 and Rhod-10 (# 341-348 and 232-239, respectively). Since these sites on rhodopsin are possible binding sites for transducin and rhodopsin kinase, an alteration in these regions would have profound effects in the dystrophic state.

Amino Acid Sequence↗
PubMed1987

Molecular cloning of the S-antigen cDNA from bovine retina.

S-antigen is the major component of the soluble proteins in the retina and the pineal, and is thought to play a regulatory role in the visual cycle. It induces experimental autoimmune uveitis (E.A.U.) in various species of laboratory animals. We have cloned the cDNA of S-antigen from bovine retina, containing the entire coding region, and determined its nucleotide sequence. The sequence consists of a 1212 nucleotide region that specific the amino acid sequence, a 368 nucleotide 5' untranslated region and a 80 nucleotide 3' untranslated region. The previously reported partial amino acid sequence defining the carboxy terminal moiety of the polypeptide, fits into our sequence. Homologies were found between the predicted amino acid sequence of S-antigen and that of alpha transducin.

Amino Acid Sequence↗
PubMed1989

Identification of a retina-specific MEKA protein as a 33 K protein.

A photoreceptor-specific MEKA protein was purified from bovine retinal soluble fraction. The purified sample was eluted as a single peak of 74 kDa protein from a Superose column, which was dissolved into three components, MEKA protein (32 kDa), beta-(36 kDa) and gamma-(10 kDa) subunits of transducin on a SDS-PAGE. From several lines of evidence, we concluded that MEKA protein is identical with a 33k phosphoprotein reported by Lee et al (1).

Animals↗
PubMed1989

The binding of G proteins to immobilized delipidated rhodopsin.

We have shown that delipidated rhodopsin immobilized on Concanavalin A-Sepharose is capable of binding transducin from crude bovine rod outer segment proteins and GIP-binding proteins (G proteins) of Go/Gi-type from solubilized bovine brain membrane as well. The binding is reversible in the presence of a solution containing 1.2% octyl-beta, D-glucopyranoside and 1 mM GTP. Also, alpha-subunits account for a large fraction of the G proteins which are bound to and then eluted from the immobilized rhodopsin. Concanavalin A-bound delipidated rhodopsin seems to be a useful model in isolating and purifying different G-proteins from crude cell lysates and solubilized membranes as well as for studying G-protein-receptor interaction.

Animals↗
PubMed1992

Differential stimulation of the GTPase activity of G-proteins by polylysine.

Polylysine, polyornithine and, to a lesser extent, polyarginine were found to stimulate the GTPase activity of the purified recombinant alpha subunit of the human G(i)-3 transducing protein alpha i-3. Optimal stimulation of 4- to 5-fold was obtained with polylysine concentrations between 1 and 20 microM, higher concentrations being inhibitory. Polylysine at similar concentrations stimulated by 50% the GTPase of transducin (GT), the vision transducing protein, but had only a very slight effect on the GTPase of the p21 product of the H-ras protooncogene. The stimulation of the alpha i-3 GTPase caused by polylysine was due to a reduction of the apparent Km for GTP from 3.8 to 1.3 microM. The stimulation by polylysine was observed at free Mg2+ concentrations below 1 microM. These results indicate that polylysine acts in a fashion similar to mastoparan and substance P in mimicking the action of an agonist-bound receptor on G-proteins.

Enzyme Activation↗
PubMed1996

Receptor-independent G protein activation may account for the stimulatory effects of first-generation H1-receptor antagonists in HL-60 cells, basophils, and mast cells.

The first-generation histamine H1-receptor antagonists, chlorpheniramine (CPHE) and diphenhydramine (DPH), may activate histamine release from basophils and mast cells. Because CPHE and DPH are cationic-amphiphilic and because several substances with such physicochemical properties activate heterotrimeric regulatory guanine nucleotide-binding proteins (G-proteins) in a receptor-independent manner, we asked the question of whether or not H1-receptor antagonists could be G-protein activators as well. In dibutyryl cAMP-differentiated HL-60 cells, CPHE and DPH increased cytosolic Ca2+ concentration and azurophilic granule release in pertussis toxin (PTX)-sensitive manners. In HL-60 membranes, PTX-sensitive stimulations of GTPase [E.C. 3.6.1.] and binding of guanosine 5'-[gamma-thio]triphosphate by H1 receptor antagonists were observed. CPHE and DPH also increased GTP hydrolysis by the purified PTX-sensitive G-protein, transducin. In all-trans-retinoic acid-differentiated HL-60 cells and rat basophilic leukemia cells (RBL 2H3 cells), H1-receptor antagonists induced, unlike in dibutyryl cAMP-differentiated HL-60 cells, Ca2+ influx without Ca2+ mobilization from intracellular stores. CPHE and DPH also induced serotonin release from RBL 2H3 cells. Our data indicate that first-generation H1-receptor antagonists are receptor-independent G-protein activators and that such a mechanism of action accounts for their stimulatory effects in HL-60 cells, basophils, and mast cells.

Animals↗
PubMed1991

Levels of mRNA encoding proteins of the cGMP cascade as a function of light environment.

The levels of the retinal mRNAs encoding opsin, the alpha subunit of rod transducin (T alpha), S-antigen (S-ag) and the gamma subunit of rod-specific cGMP-phosphodiesterase (cGMP-PDE) were measured in rats reared in cyclic light or darkness and after adaptation for different periods of time to the opposite light environment. We found that rats changed from cyclic light to darkness, gradually increased their retinal content of opsin and T alpha mRNAs but decreased their levels of S-ag mRNA. The reverse results were obtained when rats were changed from darkness to cyclic light. In contrast, the levels of retinal cGMP-PDE gamma mRNA remained unchanged in animals adapted to either of the two rearing light conditions. Our results indicate that some mRNAs encoding proteins associated with the cGMP cascade are responsive to environmental lighting and may be involved in the long term light or dark adaptive processes.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1986

Detection of the major pertussis toxin substrate of human leukocytes with antisera raised against synthetic peptides.

Antisera raised against the carboxy-terminal decapeptide (KENLKDCGLF) of transducin-alpha detected the 40 kDa, major pertussis toxin substrate of human neutrophils. The antisera also detected this protein in undifferentiated HL-60 and U937 cells, and revealed an approx. 2-fold increase in protein/mg membrane protein with differentiation into mature phagocytic cells. The results provide direct immunochemical evidence for the presence of a novel, pertussis toxin-sensitive guanine nucleotide-binding protein in human leukocytes.

Antigen-Antibody Complex↗
PubMed1988

Block of light responses of salamander rods by pertussis toxin and reversal by nicotinamide.

Transducin is the substrate for a pertussis toxin-catalyzed ADP-ribosylation in isolated retinal rod disk membranes [(1984) J. Biol. Chem. 259, 23-26]. The effects of the toxin on the light responses of intact dark-adapted rods were studied. Applied close to a rod outer segment in a retinal slice, pertussis toxin depolarized the rod by a few millivolts and produced a long-lasting depression of light responses, effects which depended on penetration of toxin into rods. Nicotinamide, an inhibitor of ADP-ribosylation, not only blocked the action of the toxin, but also reversed the effects once established. The action of nicotinamide itself on rods indicates the presence of endogenous ADP-ribosyltransferases which may constitute a control system modulating phototransduction. Inhibition of phospholipase C by neomycin had only transient effects indicating that the cGMP, rather than a phosphoinositide, pathway is primary in vertebrate phototransduction. Rapid reversal of pertussis toxin action suggests possible clinical applications of nicotinamide or congeners to the treatment of disease caused by ADP-ribosylating bacterial toxins.

Adenosine Diphosphate Ribose↗
PubMed1989

Arrestin of bovine photoreceptors reveals strong ATP binding.

The soluble protein arrestin (also named 48K-protein or retinal-S-antigen) is involved in controlling light-dependent transducin and cGMP phosphodiesterase activity in retinal rods. It is also known for its ability to induce autoimmune reactions in the eye causing the eye disease uveitis. We report here a rapid binding of ATP to arrestin with KA = 2 x 10(21) (l/mol)3 and a coordination number n = 3. This ATP binding to arrestin supports the notion of a nucleotide exchange which initiates the rapid inhibitory action of this enzyme during the primary step of vertebrate phototransduction.

Adenosine Diphosphate↗
PubMed1993

Expression of mouse rod photoreceptor cGMP phosphodiesterase gamma subunit in bacteria.

We expressed the gamma subunit of mouse rod photoreceptor cGMP phosphodiesterase (PDE) in the bacterial pGFX-2TK expression vector which produces a cleavable 40 kDa fusion protein. The fusion protein can be isolated in a one step procedure by affinity chromatography on glutathione beads. The yield of purified fusion protein is approximately 10 mg from 1 liter of bacterial culture, or about 3 mg of PDE gamma equivalent to the PDE gamma content of approximately 200,000 mouse retinas. Both the fusion protein and the cleaved PDE gamma, to which a short kinase domain remains attached, are biologically active, inhibiting activated PDE in a manner comparable to native PDE gamma. Immobilized PDE gamma binds transducin alpha subunit charged with GTP, PDE alpha and beta subunits, and, unexpectedly, arrestin (S-antigen).

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1994

GTP-dependent binding of Gi, G(o) and Gs to the gamma-subunit of the effector of Gt.

The gamma-subunit of the cGMP-phosphodiesterase (PDE gamma) of retinal rods forms a tight complex with the activated alpha-subunit of transducin (Gt alpha GTP gamma S). We observe that while PDE gamma is not the physiological effector of other G alpha subtypes, it can still detectably interact with them. This interaction is strong with Gi1 alpha and Gi3 alpha (Kd approximately 10 nM) and weaker with Go alpha and Gs alpha (Kd approximately 1 microM). For all these G alpha subtypes, similar intrinsic fluorescence changes are observed upon PDE gamma binding. Moreover, similar relative decreases in affinity are obtained when the GDP forms of Gi1 alpha, Gi3 alpha or Gt alpha are used in lieu of the GTP forms. This points to a conserved GTP-dependent effector-interaction domain.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1989

The STE4 and STE18 genes of yeast encode potential beta and gamma subunits of the mating factor receptor-coupled G protein.

The STE4 and STE18 genes are required for haploid yeast cell mating. Sequencing of the cloned genes revealed that the STE4 polypeptide shows extensive homology to the beta subunits of mammalian G proteins, while the STE18 polypeptide shows weak similarity to the gamma subunit of transducin. Null mutations in either gene can suppress the haploid-specific cell-cycle arrest caused by mutations in the SCG1 gene (previously shown to encode a protein with similarity to the alpha subunit of G proteins). We propose that the products of the STE4 and STE18 genes comprise the beta and gamma subunits of a G protein complex coupled to the mating pheromone receptors. The genetic data suggest pheromone-receptor binding leads to the dissociation of the alpha subunit from beta gamma (as shown for mammalian G proteins), and the free beta gamma element initiates the pheromone response.

Amino Acid Sequence↗
PubMed1988

Temporal disparity in pineal and retinal ontogeny.

The development of photoreceptors and two putative neurotransmitter systems in the pineal organ and retina was studied during embryogenesis in the three-spined stickleback Gasterosteus aculeatus L. The investigation was performed by aid of immunocytochemistry using well characterized antisera to the retinal proteins alpha-transducin (TD alpha) and S-antigen (SA) (photoreceptor-markers), antisera against L-glutamic acid decarboxylase (GAD), gamma-aminobutyric acid (GABA), choline-O-acetyltransferase (ChAT) and with acetylcholinesterase (AChE) histochemistry (neurotransmitter-markers). It was possible to set up the following developmental time-table concerning the first appearance of positive immuno- and enzyme-reactive cells in the pineal organ and retina: I AChE-activity and TD alpha- and SA-immunoreactive cells in the pineal organ; II GAD- and GABA-immunoreactive cells in the pineal organ and retina; ChAT immunoreactivity and AChE activity in the retina; III hatching; IV SA-immunoreactive cells in the retina. The obtained results provide good evidence that while photoreceptor cells develop much earlier in the pineal organ than in the retina, neurons develop simultaneously in the pineal organ and retina.

Acetylcholinesterase↗
PubMed1989

Identification of GTP-binding proteins in Fasciola hepatica and Schistosoma mansoni by immunoblotting.

Both the liver fluke Fasciola hepatica and the blood fluke Schistosoma mansoni have GTP-binding proteins which are part of the trans-membrane signalling system. These proteins require GTP in order to interact with the catalytic subunit of adenylate cyclase. The technique of immunoblotting was used in order to distinguish the GTP-binding proteins Gs, Gi, and Go. Immunoblotting was carried out using antisera prepared against peptides deduced from bovine cDNA clones specific for alpha or beta subunits of known G proteins. A 41-kDa Gs alpha has been identified in S. mansoni and a 42.5-kDa Gs alpha in F. hepatica. A 41-kDa Go alpha was found in both parasites. A 36-kDa G beta was identified in both parasites using antiserum made against bovine transducin.

Amino Acid Sequence↗