The Experts below are selected from a list of 219 Experts worldwide ranked by ideXlab platform
Patrick J. King - One of the best experts on this subject based on the ideXlab platform.
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A Tryptophan auxotroph ofHyoscyamus muticus lacking Tryptophan-synthase activity
Planta, 1990Co-Authors: Heinz Fankhauser, François Pythoud, Patrick J. KingAbstract:A variant clone of Hyoscyamus muticus (VIIIB9) with a specific, stable requirement for Tryptophan has been shown to have the following characteristics: (i) no accumulation of Tryptophan from anthranilic acid; (ii) growth on added Tryptophan or indole but not on anthranilic acid; (iii) accumulation of indole-3-glycerol phosphate and other indole derivatives; (iv) extractable activity of the enzymes for Tryptophan biosynthesis, including the partial reaction 2 of Tryptophan synthase but not reactions 1 or 3. Thus these data provide in-vivo evidence for the existence of a two-component, bacterial-type Tryptophan synthase in plants, the Tryptophan auxotrophy of VIIIB9 probably being the consequence of a mutation in the α-subunit of the Tryptophan-synthase complex.
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A Tryptophan auxotroph of Hyoscyamus muticus lacking Tryptophan-synthase activity
Planta, 1990Co-Authors: Heinz Fankhauser, François Pythoud, Patrick J. KingAbstract:A variant clone of Hyoscyamus muticus (VIIIB9) with a specific, stable requirement for Tryptophan has been shown to have the following characteristics: (i) no accumulation of Tryptophan from anthranilic acid; (ii) growth on added Tryptophan or indole but not on anthranilic acid; (iii) accumulation of indole-3-glycerol phosphate and other indole derivatives; (iv) extractable activity of the enzymes for Tryptophan biosynthesis, including the partial reaction 2 of Tryptophan synthase but not reactions 1 or 3. Thus these data provide in-vivo evidence for the existence of a two-component, bacterial-type Tryptophan synthase in plants, the Tryptophan auxotrophy of VIIIB9 probably being the consequence of a mutation in the α-subunit of the Tryptophan-synthase complex.
Fernando C Reinach - One of the best experts on this subject based on the ideXlab platform.
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regulatory properties of recombinant tropomyosins containing 5 hydroxyTryptophan ca2 binding to troponin results in a conformational change in a region of tropomyosin outside the troponin binding site
Biochemistry, 1999Co-Authors: Chuck S Farah, Fernando C ReinachAbstract:We have introduced Tryptophan codons at different positions of the chicken α-tropomyosin cDNA (Monteiro, P. B., Lataro, R. C., Ferro, J. A., and Reinach, F. C. (1994) J. Biol. Chem. 269, 10461−10466) and employed a trp auxotrophic Escherichia coli strain to express the proteins in media containing either normal Tryptophan, 5-hydroxytrptophan, or 7-azaTryptophan. The fluorescence of these latter two Tryptophan analogues is excitable at 312−315 nm at which the natural fluorescence of other thin filament proteins (actin, troponin) is not excited. The recombinant tropomyosins have Tryptophans or analogues located at amino acid positions 90, 101, 111, 122, or 185 of the protein, all on the external surface of the tropomyosin coiled-coil (positions “c” or “f” of the hydrophobic heptad repeat). The first four mutations are located within the third actin-binding zone of tropomyosin, a region not expected to interact directly with troponin or with neighboring tropomyosin molecules in muscle thin filaments, while p...
D J Madge - One of the best experts on this subject based on the ideXlab platform.
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the effects of a novel and selective inhibitor of Tryptophan 2 3 dioxygenase on Tryptophan and serotonin metabolism in the rat
Biochemical Pharmacology, 1995Co-Authors: M Salter, Robert Hazelwood, Christopher I Pogson, Ramachandran Iyer, D J MadgeAbstract:Abstract The effects of a novel inhibitor 680C91 (( E )-6-fluoro-3-[2-(3-pyridyl)vinyl]-1 H -indole) of the key enzyme of Tryptophan catabolism Tryptophan 2,3-dioxygenase (TDO) (EC 1.13.11.11), were examined on Tryptophan catabolism in vitro and in vivo and on brain levels of Tryptophan, serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA). 680C91 was a potent ( K i = 51 nM) and selective TDO inhibitor with no inhibitory activity against indoleamine 2,3-dioxygenase (EC 1.13.11.17), monoamine oxidase A and B, 5-HT uptake and 5-HT 1A,1D,2A and 2C receptors at a concentration of 10 μM. 680C91 had no effect on the binding of Tryptophan to serum albumin in plasma and inhibited TDO competitively with respect to its substrate Tryptophan. 680C91 inhibited the catabolism of Tryptophan by rat liver cells and rat liver perfused in situ . The catabolism of l -[ring-2- 14 C]-Tryptophan and a load dose of Tryptophan (100 mg/kg) in vivo were inhibited by prior administration of 680C91. Administration of 680C91 alone produced marked increases in brain Tryptophan, 5-HT and 5-HIAA. A load dose of Tryptophan (100 mg/kg), producing increases in brain Tryptophan 4-fold greater than that seen with 680C91, did not increase brain 5-HT and 5-HIAA to levels greater than those seen with 680C91 and produced a shorter-lasting increase in these parameters. These data therefore demonstrate the importance of TDO as a regulator of whole-body Tryptophan catabolism and brain levels of Tryptophan and 5-HT and suggest that a greater antidepressant efficacy might be achieved with inhibitors of TDO than Tryptophan administration alone.
Heinz Fankhauser - One of the best experts on this subject based on the ideXlab platform.
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A Tryptophan auxotroph ofHyoscyamus muticus lacking Tryptophan-synthase activity
Planta, 1990Co-Authors: Heinz Fankhauser, François Pythoud, Patrick J. KingAbstract:A variant clone of Hyoscyamus muticus (VIIIB9) with a specific, stable requirement for Tryptophan has been shown to have the following characteristics: (i) no accumulation of Tryptophan from anthranilic acid; (ii) growth on added Tryptophan or indole but not on anthranilic acid; (iii) accumulation of indole-3-glycerol phosphate and other indole derivatives; (iv) extractable activity of the enzymes for Tryptophan biosynthesis, including the partial reaction 2 of Tryptophan synthase but not reactions 1 or 3. Thus these data provide in-vivo evidence for the existence of a two-component, bacterial-type Tryptophan synthase in plants, the Tryptophan auxotrophy of VIIIB9 probably being the consequence of a mutation in the α-subunit of the Tryptophan-synthase complex.
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A Tryptophan auxotroph of Hyoscyamus muticus lacking Tryptophan-synthase activity
Planta, 1990Co-Authors: Heinz Fankhauser, François Pythoud, Patrick J. KingAbstract:A variant clone of Hyoscyamus muticus (VIIIB9) with a specific, stable requirement for Tryptophan has been shown to have the following characteristics: (i) no accumulation of Tryptophan from anthranilic acid; (ii) growth on added Tryptophan or indole but not on anthranilic acid; (iii) accumulation of indole-3-glycerol phosphate and other indole derivatives; (iv) extractable activity of the enzymes for Tryptophan biosynthesis, including the partial reaction 2 of Tryptophan synthase but not reactions 1 or 3. Thus these data provide in-vivo evidence for the existence of a two-component, bacterial-type Tryptophan synthase in plants, the Tryptophan auxotrophy of VIIIB9 probably being the consequence of a mutation in the α-subunit of the Tryptophan-synthase complex.
Robert W. Woody - One of the best experts on this subject based on the ideXlab platform.
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Contributions of Tryptophan side chains to the far-ultraviolet circular dichroism of proteins
European Biophysics Journal, 1994Co-Authors: Robert W. WoodyAbstract:It has often been assumed that the role of aromatic side chains in the far-ultraviolet region of protein circular dichroism (CD) is negligible. However, some proteins have positive CD bands in the 220–230 nm region which are almost certainly due to aromatic side chains. The contributions to the CD of interactions between Tryptophan side chains and the nearest neighbor peptide groups have been studied, focusing on the indole B_b transition which occurs near 220 nm. Calculations on idealized peptide conformations show that the CD depends strongly on both backbone and side-chain conformation. Because of the low symmetry of indole, rotation about the C_βC_γ bond (dihedral angle χ_2) by 180° generally leads to large changes in the CD, often causing the B_b band to reverse sign. When side-chain conformational preferences are taken into account, there is no strong bias for either positive or negative B_b rotational strengths. The observation that simple Tryptophan derivatives such as N-acetyl-L-Tryptophan methylamide have positive CD near 220 nm implies either that these derivatives prefer the α_R region over the β region, or that there is little preference for χ_2 < 180° over χ_2 > 180°. Nearest-neighbor-only calculations on individual Tryptophans in 15 globular proteins also reveal a small bias toward positive B_b bands. Rotational strengths of the B_b transition for some conformations can be as large as ∼ 1.0 Debye-Bohr magnetons in magnitude, corresponding to maximum molar ellipticities greater than 10^5 degcm^2/dmol. Although a substantial amount of cancellation occurs in most of the examples considered here, such CD contributions could be significant, especially in proteins of low helix content.
