Dye-sensitized selective photooxidation of methioxine

Jori, Giulio; Galiazzo, G.; Marzotto, A.; Scoffone, Ernesto

doi:10.1016/0005-2795(68)90252-3

Cited by 80 publications

(32 citation statements)

References 28 publications

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“…As the oxidation of methionine residues prevents the reaction with CNBr from taking place, 2-mercaptoethanol or dithiothreitol was used to minimize methionine sulphoxide formation during purification and storage of the enzymes (Jori et al, 1968). N. crassa enzyme.…”

Section: Digestion With Cnbrmentioning

confidence: 99%

Identification of the active-site lysine residues of two biosynthetic 3-dehydroquinases

Chaudhuri

Duncan

Graham

et al. 1991

Biochemical Journal

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The lysine residues involved in Schiff-base formation at the active sites of both the 3-dehydroquinase component of the pentafunctional arom enzyme of Neurospora crassa and of the monofunctional 3-dehydroquinase of Escherichia coli were labelled by treatment with 3-dehydroquinate in the presence of NaB3H4. Radioactive peptides were isolated by h.p.l.c. following digestion with CNBr (and in one case after further digestion with trypsin). The sequence established for the N. crassa peptide was ALQHGDVVKLVVGAR, and that for the E. coli peptide was QSFDADIPKIA. An amended nucleotide sequence for the E. coli gene (aroD) that encode 3-dehydroquinase is also presented, along with a revised alignment of the deduced amino acid sequences for the biosynthetic enzymes.

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Section: Digestion With Cnbrmentioning

confidence: 99%

Identification of the active-site lysine residues of two biosynthetic 3-dehydroquinases

Chaudhuri

Duncan

Graham

et al. 1991

Biochemical Journal

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“…C.V. is known to specifically oxidize SH-groups in proteins to SO3-groups by photosensitization (1,9). Fig.…”

Section: Resultsmentioning

confidence: 99%

Functional Asymmetry in Excitable Surface Membrane of Protoplasmic Droplet Isolated from <I>Nitella</I> by Photosensitized Oxidation

Ueda

Muratsugu

Kobatake

1976

Cell Struct. Funct.

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ABSTRACT.Photooxidations of protoplasmic droplets of Nitella were performed by crystal violet (C.V.), rose bengal (R.B.) and methylene blue (M.B.) from the inside or outside of the membrane.Various physical properties of the droplet were examined. External treatment of the membrane by C.V. induced a temporary increase of resistance and a gradual depolarization of the membrane potential. Excitability disappeared after the depolarization, but the surface tension remained constant. Both membrane potential and resistance remained constant when the droplet was modified by C.V. from the inside, and the excitability was retained. Tension at the surface, however, decreased sharply by a factor of 100. Internal application of R.B. decreased resistance and depolarized the membrane potential by a maximum 20 mV. External treatment with R.B. caused a temporary decrease of resistance with depolarization by about 100 mV. Adsorption of M.B. on the surface membrane led to a decrease in resistance without changing the membrane potential under light illumination, and this was followed by abrupt depolarization. These results indicate that membrane potential and excitability of the protoplasmic droplet are governed largely by the structure at the outermost surface between the protoplasm and external solution and that the tension at the surface is maintained by the internal structure of the protoplasm. 155 Plasma membranes of cells are generally located in an extremely asymmetric environment, i.e., the concentration differences of ionic species on the two sides of the membrane vary by a factor of over 100, the electrical potential differs by 50 to 100 mV and the intracellular potential is negative with respect to the external solution. It is not unreasonable to assume that membranes may have a high anisotropic structure.The asymmetric organization of proteins in erythrocyte membrane was examined by Bender, Garan and Berg (2), Bretcher (3), Phyllips and Morison (12), Sergest et al. (13) and Zwaal, Roelofsen and Colley (20) by treating the membrane with non-penetrating reagents. Asymmetric distributions of phospholipids were reported by Bretcher (4), Stanley, Gordesky and Marinetti (14) and Zwaal, Roelofsen and Colley (20) who studied erythrocyte membranes by digesting phospholipids with specific enzymes. Among these findings, it is interesting to note that the molecular composition of both the proteins and phospholipids differs between the intact and ghost cell membranes (15).Functional asymmetry in the excitable membrane has been studied only in internally perfused squid giant axons. Tasaki (16) demonstrated that internal and external

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“…A 45% decrease of catalytic efficiency was also observed upon irradiation of c~ochrome c, which had been alkylated at Met-65, in order to prevent photooxidative attack on this residue 193 : the amino acid analysis of this irradiated sample did not differ significantly from that obtained for the alkylated nonirradiated protein (table 1). In all cases, treatment of photooxidized cytochromes with 2-mercaptoe~~ol (which is known to reduce sulfoxides to thioethers [ 131) resulted in a complete recovery of biological activity.…”

Section: Resultsmentioning

confidence: 99%

“…The reaction of cytochrome c with iodoacetic acid to obtain the alkylation of His-33 and Met-65 was carried out by previously published methods [7]. The methods for performing the amino acid analyses and for determining the electron transport activity have been described in previous papers [8,9]. In the case of the alkylated derivatives of cytochrome c, unaffected methionines were determined after performic acid oxidation [lo] .…”

Section: Methodsmentioning

confidence: 99%