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Rajakrishnan Veluthakal - One of the best experts on this subject based on the ideXlab platform.
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Rho Guanosine Diphosphate-dissociation inhibitor plays a negative modulatory role in glucose-stimulated insulin secretion.
Diabetes, 2005Co-Authors: Anjaneyulu Kowluru, Rajakrishnan VeluthakalAbstract:Extant studies have implicated the Rho subfamily of Guanosine triphosphate–binding proteins (G-proteins; e.g., Rac1) in physiological insulin secretion from isolated β-cells. However, very little is known with regard to potential regulation by G-protein regulatory factors (e.g., the Guanosine Diphosphate–dissociation inhibitor [GDI]) of insulin secretion from the islet β-cell. To this end, using Triton X-114 phase partition, co-immunoprecipitation, and sucrose density gradient centrifugation approaches, we report coexistence of GDI with Rac1 in insulin-secreting β-cells (INS cells). Overexpression of wild-type GDI significantly inhibited glucose-induced, but not KCl- or mastoparan-induced, insulin secretion from INS cells. Furthermore, glucose-stimulated insulin secretion (GSIS) was significantly increased in INS cells in which expression of GDI was inhibited via the small interfering RNA–mediated knockdown approach. Together, these data appear to suggest an inhibitory role for GDI in the glucose metabolic signaling cascade, which may be relevant for GSIS.
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Rho Guanosine Diphosphate-Dissociation Inhibitor Plays a Negative Modulatory Role in Glucose-Stimulated
2005Co-Authors: Anjaneyulu Kowluru, Rajakrishnan VeluthakalAbstract:Extant studies have implicated the Rho subfamily of Guanosine triphosphate– binding proteins (G-proteins; e.g., Rac1) in physiological insulin secretion from isolated -cells. However, very little is known with regard to potential regulation by G-protein regulatory factors (e.g., the Guanosine Diphosphate– dissociation inhibitor [GDI]) of insulin secretion from the islet -cell. To this end, using Triton X-114 phase partition, co-immunoprecipitation, and sucrose density gradient centrifugation approaches, we report coexistence of GDI with Rac1 in insulin-secreting -cells (INS cells). Overexpression of wild-type GDI significantly inhibited glucose-induced, but not KCl- or mastoparan-induced, insulin secretion from INS cells. Furthermore, glucose-stimulated insulin secretion (GSIS) was significantly increased in INS cells in which expression of GDI was inhibited via the small interfering RNA–mediated knockdown approach. Together, these data appear to suggest an inhibitory role for GDI in the glucose metabolic signaling cascade, which may be relevant for GSIS. Diabetes 54:3523–3529, 2005
Michael Yarus - One of the best experts on this subject based on the ideXlab platform.
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5‘-RNA Self-Capping from Guanosine Diphosphate†
Biochemistry, 1997Co-Authors: Faqing Huang, Michael YarusAbstract:A selected RNA (isolate 6) efficiently catalyzes a self-capping reaction with free GDP, yielding the same 5‘-capped structure as is formed by protein GTP:RNA guanylyltransferase. This unexplored RNA-catalyzed reaction type involving nucleophilic attack on phosphate by phosphate adds to the variety of possible postsynthetic RNA-catalyzed RNA modifications. The selected RNA requires only Ca2+ for activation and has a broad active pH range of 4.5−9.0. The RNA also has a 5‘-pyrophosphatase activity.
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5 rna self capping from Guanosine Diphosphate
Biochemistry, 1997Co-Authors: Faqing Huang, Michael YarusAbstract:A selected RNA (isolate 6) efficiently catalyzes a self-capping reaction with free GDP, yielding the same 5‘-capped structure as is formed by protein GTP:RNA guanylyltransferase. This unexplored RNA-catalyzed reaction type involving nucleophilic attack on phosphate by phosphate adds to the variety of possible postsynthetic RNA-catalyzed RNA modifications. The selected RNA requires only Ca2+ for activation and has a broad active pH range of 4.5−9.0. The RNA also has a 5‘-pyrophosphatase activity.
J Oro - One of the best experts on this subject based on the ideXlab platform.
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synthesis of the coenzymes adenosine Diphosphate glucose Guanosine Diphosphate glucose and cytidine diphosphoethanolamine under primitive earth conditions
Journal of Molecular Evolution, 1991Co-Authors: A Mar, J OroAbstract:The nonenzymatic synthesis of the coenzymes adenosine Diphosphate glucose (ADPG), Guanosine Diphosphate glucose (GDPG), and cytidine diphosphoethanolamine (CDP-ethanolamine) has been carried out under conditions considered to have been prevalent on the early Earth. The production of these compounds was performed by allowing simple precursor molecules to react under aqueous solutions, at moderate temperatures and short periods of time, with mediation by cyanamide or urea. These two condensing agents are considered to have been present in significant amounts on the primitive Earth and have been previously used in the nonenzymatic synthesis of several other important biochemical compounds. In our experiments, ADPG was obtained by heating glucose-1-phosphate (G1P) and ATP in the presence of cyanamide for 24 h at 70 degrees C. The reaction of G1P and GTP under the same conditions yielded GDPG. The cyanamide-mediated production of CDP-ethanolamine was carried out by reacting a mixture of ethanolamine phosphate and CTP for 24 h at 70 degrees C. The separation and identification of the reaction products was carried out by paper chromatography, thin-layer chromatography, high performance thin-layer chromatography, high performance liquid chromatography, both normal and reverse-phase, UV spectroscopy, enzymatic assays, and acid hydrolysis. Due to the mild conditions employed, and to the relative ease of these reactions, these studies offer a simple attractive system for the nonenzymatic synthesis of phosphorylated high-energy metabolic intermediates under conditions considered to have been prevalent on the ancient Earth.
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Synthesis of the coenzymes adenosine Diphosphate glucose, Guanosine Diphosphate glucose, and cytidine diphosphoethanolamine under primitive earth conditions
Journal of Molecular Evolution, 1991Co-Authors: A Mar, J OroAbstract:The nonenzymatic synthesis of the coenzymes adenosine Diphosphate glucose (ADPG), Guanosine Diphosphate glucose (GDPG), and cytidine diphosphoethanolamine (CDP-ethanolamine) has been carried out under conditions considered to have been prevalent on the early Earth. The production of these compounds was performed by allowing simple precursor molecules to react under aqueous solutions, at moderate temperatures and short periods of time, with mediation by cyanamide or urea. These two condensing agents are considered to have been present in significant amounts on the primitive Earth and have been previously used in the nonenzymatic synthesis of several other important biochemical compounds. In our experiments, ADPG was obtained by heating glucose-1-phosphate (G1P) and ATP in the presence of cyanamide for 24 h at 70°C. The reaction of G1P and GTP under the same conditions yielded GDPG. The cyanamide-mediated production of CDP-ethanolamine was carried out by reacting a mixture of ethanolamine phosphate and CTP for 24 h at 70°C. The separation and identification of the reaction products was carried out by paper chromatography, thin-layer chromatography, high performance thin-layer chromatography, high performance liquid chromatography, both normal and reverse-phase, UV spectroscopy, enzymatic assays, and acid hydrolysis. Due to the mild conditions employed, and to the relative ease of these reactions, these studies offer a simple attractive system for the nonenzymatic synthesis of phosphorylated high-energy metabolic intermediates under conditions considered to have been prevalent on the ancient Earth.
T.m. Vuong - One of the best experts on this subject based on the ideXlab platform.
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Kinetic analysis of the activation of transducin by photoexcited rhodopsin. Influence of the lateral diffusion of transducin and competition of Guanosine Diphosphate and Guanosine triphosphate for the nucleotide site.
Biophysical journal, 1992Co-Authors: Franz Bruckert, M. Chabre, T.m. VuongAbstract:The activation of transducin (T) by photoexcited rhodopsin (R*) is kinetically dissected within the framework of Michaelis-Menten enzymology, taking transducin as substrate of the enzyme R*. The light scattering "release" signal (Vuong, T.M., M. Chabre, and L. Stryer, 1984, Nature (Lond.). 311:659–661) was used to monitor the kinetics of transducin activation at 20 degrees C. In addition, the influence of nonuniform distributions of R* on these activation kinetics is also explored. Sinusoidal patterns of R* were created with interference fringes from two crossed laser beams. Two characteristic times were extracted from the Michaelis-Menten analysis: t(form), the diffusion-related time needed to form the enzyme-substrate R*-transducin is 0.25 +/- 0.1 ms, and T(cat), the time taken by R* to perform the chemistry of catalysis on transducin is 1.2 +/- 0.2 ms, in the absence of added Guanosine Diphosphate (GDP) and at saturating levels of Guanosine triphosphate (GTP). With t(form) being but 20% of the total activation time t(form) + t(cat), transducin activation by R* is not limited by lateral diffusion. This is further borne out by the observation that uniform and sinusoidal patterns of R* elicited release signals of indistinguishable kinetics. When (GDP) = (GTP) = 500 microM, t(cat) is lengthened twofold. As the in vivo GDP and GTP levels are comparable, the exchange of nucleotides may well be the rate-limiting process.
Gavin J Miller - One of the best experts on this subject based on the ideXlab platform.
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Inhibition of the GDP-d-Mannose Dehydrogenase from Pseudomonas aeruginosa Using Targeted Sugar Nucleotide Probes.
ACS chemical biology, 2020Co-Authors: Laura Beswick, Eleni Dimitriou, Sanaz Ahmadipour, Ayesha Zafar, Martin Rejzek, Jóhannes Reynisson, Robert A Field, Gavin J MillerAbstract:Sufferers of cystic fibrosis are at extremely high risk for contracting chronic lung infections. Over their lifetime, one bacterial strain in particular, Pseudomonas aeruginosa, becomes the dominant pathogen. Bacterial strains incur loss-of-function mutations in the mucA gene that lead to a mucoid conversion, resulting in copious secretion of the exopolysaccharide alginate. Strategies that stop the production of alginate in mucoid Pseudomonas aeruginosa infections are therefore of paramount importance. To aid in this, a series of sugar nucleotide tools to probe an enzyme critical to alginate biosynthesis, Guanosine Diphosphate mannose dehydrogenase (GMD), have been developed. GMD catalyzes the irreversible formation of the alginate building block, Guanosine Diphosphate mannuronic acid. Using a chemoenzymatic strategy, we accessed a series of modified sugar nucleotides, identifying a C6-amide derivative of Guanosine Diphosphate mannose as a micromolar inhibitor of GMD. This discovery provides a framework for wider inhibition strategies against GMD to be developed.