scholarly journals Specific Binding of Protoporphyrin IX to a Membrane-Bound 63 Kilodalton Polypeptide in Cucumber Cotyledons Treated with Diphenyl Ether-Type Herbicides

1991 ◽  
Vol 96 (2) ◽  
pp. 432-437 ◽  
Author(s):  
Ryo Sato ◽  
Hiromichi Oshio ◽  
Hiroyuki Koike ◽  
Yorinao Inoue ◽  
Shigeo Yoshida ◽  
...  
Keyword(s):  
Specific Binding ◽  
Diphenyl Ether ◽  
Protoporphyrin Ix ◽  
Membrane Bound ◽  
Cucumber Cotyledons

Molecular Aspects of Herbicide Action on Protoporphyrinogen Oxidase

1993 ◽  
Vol 48 (3-4) ◽  
pp. 326-333 ◽  
Author(s):  
Beate Nicolaus ◽  
Gerhard Sandmann ◽  
Peter Böger
Keyword(s):  
Diphenyl Ether ◽  
Protoporphyrin Ix ◽  
Protoporphyrinogen Oxidase ◽  
Relative Specificity ◽  
Oxidase Inhibition ◽  
Dilution Experiments ◽  
Membrane Bound ◽  
The Common ◽  
Molecular Aspects ◽  
Derivatives Of

Abstract Protoporphyrinogen oxidase, the last enzyme of the common tetrapyrrole biosynthetic pathway, is inhibited by several peroxidizing compounds resulting in accumulation of photodynamic tetrapyrroles, mainly protoporphyrin IX. The inhibition characteristics of two chemi­cally unrelated compounds were studied using membrane bound protoporphyrinogen oxidase from corn etioplasts. As shown by Lineweaver-Burk-analysis, the inhibition of enzyme activity by the diphenyl ether oxyfluorfen and the cyclic imide MCI 15 are competitive with respect to the substrate. The competitive interaction of protoporphyrinogen and the two chemically un­related inhibitors indicate a relative specificity of the binding site. The reversibility of oxyfluorfen inhibition was evaluated by dilution experiments and was shown to be independent of the presence of DTT. The analysis of structure-activity-relationship on protoporphyrinogen oxidase inhibition was investigated with para-substituted derivatives of phenyl-3,4,5,6-tetrahydro-phthalimides. The results obtained by QSAR -calculation yielded a good correlation of the inhibitory activity determined by the lipophilicity of the para-substituent. These data point to one binding region of the inhibitors within a lipophilic environment associated with the active center of the enzyme.

Oxyfluorfen and Lipid Peroxidation: Protein Damage as a Phytotoxic Consequence

Weed Science ◽  
1985 ◽  
Vol 33 (6) ◽  
pp. 766-770 ◽  
Author(s):  
Karl J. Kunert ◽  
Carmen Homrighausen ◽  
Herbert Böhme ◽  
Peter Böger
Keyword(s):  
Lipid Peroxidation ◽  
Cytochrome C ◽  
Diphenyl Ether ◽  
Photosynthetic Electron Transport ◽  
Water Soluble ◽  
Cytochrome F ◽  
Protein Damage ◽  
Protein Loss ◽  
Membrane Bound

Protein damage, as a primary phytotoxic consequence of in vivo lipid peroxidation, induced by the diphenyl ether herbicide oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene] at a concentration of 10 μM, was measured with the green algaScenedesmus acutus. In the light, water-soluble proteins are destroyed by a herbicide-induced peroxidation process that can be detected by production of fluorescent products and loss of specific amino acid residues of proteins. The water-soluble cytochrome c-553 and the membrane-bound cytochrome f-553, components of the photosynthetic electron transport, were specifically used as sensitive markers for protein damage, measured as decrease of redox reactions of the cytochromes. Under peroxidizing conditions, destruction of the algal cytochrome c is significantly higher than destruction of membrane-bound components, such as cytochrome f and chlorophyll. Protection against protein loss is achieved by the nonbiological antioxidant ethoxyquin (1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline) or the photosynthesis inhibitor diuron [N′-(3,4-dichlorophenyl)-N,N-dimethylurea].

Processing of receptor-bound somatostatin: internalization and degradation by pancreatic acini

1987 ◽  
Vol 252 (4) ◽  
pp. G535-G542 ◽  
Author(s):  
N. Viguerie ◽  
J. P. Esteve ◽  
C. Susini ◽  
N. Vaysse ◽  
A. Ribet
Keyword(s):  
Plasma Membrane ◽  
Plasma Membranes ◽  
Specific Binding ◽  
Specific Radioactivity ◽  
Pancreatic Acinar Cells ◽  
Nuclear Fraction ◽  
Pancreatic Acini ◽  
Specific Binding Sites ◽  
Membrane Bound ◽  
Membrane Level

We have previously demonstrated the presence of specific binding sites for somatostatin on plasma membranes from pancreatic acinar cells. In the present study we attempted to characterize the fate of receptor-bound 125I-[Tyr11]somatostatin. Internalization of somatostatin was rapid (reaching a plateau at 20% of the cell-associated specific radioactivity) and temperature dependent. To follow the processing of bound somatostatin, acini were incubated with 125I-[Tyr11]somatostatin at 5 degrees C during 16 h then, after washing, incubated at 37 degrees C for 90 min in fresh medium. Surface-bound somatostatin decreased rapidly, whereas radioactivity increased in the cell interior and the incubation medium. Intracellular and membrane-bound radioactivity was mainly intact 125I-[Tyr11]somatostatin. Degradation occurred at the plasma membrane level and led to iodotyrosine production. After 15 min of incubation, 15% of the initially surface-bound 125I-[Tyr11]somatostatin was compartmentalized within the cell, mainly in the microsomal fraction. After 30 min, a significant increase in radioactivity appeared in the nuclear fraction. These results indicate that the major part of somatostatin cellular degradation takes place at the plasma membrane level. Within the cell, somatostatin is routed to the nucleus via particular fractions sedimenting with microsomal vesicles.

scholarly journals Is there a role for tau glutathione transferases in tetrapyrrole metabolism and retrograde signalling in plants?

2020 ◽  
Vol 375 (1801) ◽  
pp. 20190404 ◽  
Author(s):  
Elodie Sylvestre-Gonon ◽  
Mathieu Schwartz ◽  
Jean-Michel Girardet ◽  
Arnaud Hecker ◽  
Nicolas Rouhier
Keyword(s):  
Protoporphyrin Ix ◽  
Membrane Transporters ◽  
Glutathione Transferases ◽  
Limited Information ◽  
Tight Control ◽  
Porphyrin Derivatives ◽  
Retrograde Signalling ◽  
Tetrapyrrole Metabolism ◽  
Membrane Bound ◽  
Membrane Bound Enzymes

In plants, tetrapyrrole biosynthesis occurs in chloroplasts, the reactions being catalysed by stromal and membrane-bound enzymes. The tetrapyrrole moiety is a backbone for chlorophylls and cofactors such as sirohaems, haems and phytochromobilins. Owing to this diversity, the potential cytotoxicity of some precursors and the associated synthesis costs, a tight control exists to adjust the demand and the fluxes for each molecule. After synthesis, haems and phytochromobilins are incorporated into proteins found in other subcellular compartments. However, there is only very limited information about the chaperones and membrane transporters involved in the trafficking of these molecules. After summarizing evidence indicating that glutathione transferases (GST) may be part of the transport and/or degradation processes of porphyrin derivatives, we provide experimental data indicating that tau glutathione transferases (GSTU) bind protoporphyrin IX and haem moieties and use structural modelling to identify possible residues responsible for their binding in the active site hydrophobic pocket. Finally, we discuss the possible roles associated with the binding, catalytic transformation (i.e. glutathione conjugation) and/or transport of tetrapyrroles by GSTUs, considering their subcellular localization and capacity to interact with ABC transporters. This article is part of the theme issue ‘Retrograde signalling from endosymbiotic organelles’.

scholarly journals Global marine pollutants inhibit P-glycoprotein: Environmental levels, inhibitory effects, and cocrystal structure

2016 ◽  
Vol 2 (4) ◽  
pp. e1600001 ◽  
Author(s):  
Sascha C. T. Nicklisch ◽  
Steven D. Rees ◽  
Aaron P. McGrath ◽  
Tufan Gökirmak ◽  
Lindsay T. Bonito ◽  
...  
Keyword(s):  
Organic Pollutants ◽  
Persistent Organic Pollutants ◽  
Polybrominated Diphenyl Ethers ◽  
Specific Binding ◽  
Diphenyl Ether ◽  
Environmental Toxicants ◽  
Glycoprotein P ◽  
P Glycoprotein ◽  
Defense Protein ◽  
Cocrystal Structure

The world’s oceans are a global reservoir of persistent organic pollutants to which humans and other animals are exposed. Although it is well known that these pollutants are potentially hazardous to human and environmental health, their impacts remain incompletely understood. We examined how persistent organic pollutants interact with the drug efflux transporter P-glycoprotein (P-gp), an evolutionarily conserved defense protein that is essential for protection against environmental toxicants. We identified specific congeners of organochlorine pesticides, polychlorinated biphenyls, and polybrominated diphenyl ethers that inhibit mouse and human P-gp, and determined their environmental levels in yellowfin tuna from the Gulf of Mexico. In addition, we solved the cocrystal structure of P-gp bound to one of these inhibitory pollutants, PBDE (polybrominated diphenyl ether)–100, providing the first view of pollutant binding to a drug transporter. The results demonstrate the potential for specific binding and inhibition of mammalian P-gp by ubiquitous congeners of persistent organic pollutants present in fish and other foods, and argue for further consideration of transporter inhibition in the assessment of the risk of exposure to these chemicals.

scholarly journals Protoporphyrinogen oxidase as a molecular target for diphenyl ether herbicides

1989 ◽  
Vol 260 (1) ◽  
pp. 231-235 ◽  
Author(s):  
M Matringe ◽  
J M Camadro ◽  
P Labbe ◽  
R Scalla
Keyword(s):  
Zea Mays ◽  
Solanum Tuberosum ◽  
Diphenyl Ether ◽  
Protoporphyrin Ix ◽  
Molecular Target ◽  
Plant Tissues ◽  
Mitochondrial Membranes ◽  
Protoporphyrinogen Oxidase ◽  
Cellular Target

Diphenyl ether herbicides induce an accumulation of protoporphyrin IX in plant tissues. By analogy to human porphyria, the accumulation could be attributed to decreased (Mg or Fe)-chelatase or protoporphyrinogen oxidase activities. Possible effects of acifluorfen-methyl on these enzymes were investigated in isolated corn (maize, Zea mays) etioplasts, potato (Solanum tuberosum) and mouse mitochondria, and yeast mitochondrial membranes. Acifluorfen-methyl was strongly inhibitory to protoporphyrinogen oxidase activities whatever their origins [concn. causing 50% inhibition (IC50) = 4 nM for the corn etioplast enzyme]. By contrast, it was roughly 100,000 times less active on (Mg or Fe)-chelatase activities (IC50 = 80-100 microM). Our results lead us to propose protoporphyrinogen oxidase as a cellular target for diphenyl ether herbicides.

scholarly journals An investigation of sites that bind human somatotropin (growth hormone) in the liver of the pregnant rabbit

1981 ◽  
Vol 198 (3) ◽  
pp. 605-614 ◽  
Author(s):  
H F Cadman ◽  
M Wallis
Keyword(s):  
Growth Hormone ◽  
Binding Sites ◽  
Specific Binding ◽  
Bovine Somatotropin ◽  
Scatchard Analysis ◽  
Single Class ◽  
Pregnant Rabbit ◽  
Membrane Bound ◽  
Ovine Prolactin ◽  
Triton X

The binding of 125I-labelled human somatotropin (growth hormone) to a crude membrane preparation from the liver of pregnant rabbit, and to receptors solubilized from this fraction by Triton X-100, was dependent on time, temperature and receptor concentration. At 4 degrees C a steady state was reached after 20 h, and maximum specific binding (as a percentage of total tracer added) was approx. 50% for both membrane-bound and solubilized receptors. Solubilization did not significantly affect the binding properties of the receptor at low concentrations of Triton X-100 (less than 0.05%, v/v, in the assay tube). However, at higher concentrations (approx. 0.1%, v/v), the detergent lowered the ability of some hormones, for example ovine prolactin, to displace 125I-labelled human somatotropin, but did not affect other hormones such as bovine somatotropin. Some somatogenic hormones, such as bovine somatotropin, and some lactogenic hormones, such as ovine prolactin, displaced 125I-labelled human somatotropin from membrane-bound and solubilized receptor preparations. Furthermore, 85% of 125I-labelled bovine somatotropin was displaced from membrane-bound receptors by ovine prolactin, and 125I-labelled ovine prolactin was almost completely displaced by bovine somatotropin. Scatchard analysis of the binding data for human somatotropin suggested a single class of binding sites in the membrane-bound receptor preparation, with an affinity (Ka) of 1.9 X 10(9) M-1 and a capacity of 1726 fmol/mg of protein; these values were slightly increased by solubilization (Ka = 3.2 X 10(9) M-1, capacity = 2103 fmol/mg of protein). Scatchard analysis of binding to membrane-bound receptors also indicated a single class of high-affinity binding sites for bovine somatotropin (Ka = 4.8 X 10(9) M-1, capacity = 769 fmol/mg) and for ovine prolactin (Ka = 6.1 X 10(9) M-1, capacity = 187 fmol/mg).

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