Binding of tetrodotoxin and saxitoxin to sodium channels

1975 ◽  
Vol 270 (908) ◽  
pp. 319-336 ◽  
Keyword(s):  
Sodium Channels ◽  
Specific Binding ◽  
Chemical Characterization ◽  
Nerve Fibres ◽  
Myelinated Nerve ◽  
Channel Density ◽  
Binding Curve ◽  
Measurable Property ◽  
Binding Component

A useful first step in any chemical characterization of the sodium channels in nerve membrane would clearly be the identification of some measurable property of the channel that does not depend on the intactness of the tissue. To this end, tetrodotoxin and saxitoxin, which bind specifically to sodium channels, have been tritiated and their binding to rabbit, lobster and garfish non-myelinated nerve fibres examined. In each case, a component of the binding curve was found that saturated at concen­ trations of a few nanomolar. In addition, non-specific binding, indicated by a linear dependence of the amount bound on concentration, occurred. A solubilized membrane preparation from garfish nerve shows the same specific binding component as that of the intact nerve. The saturable component of binding seems to reflect the sodium channel density in nerve, and this is extremely small, being about 27/m 2 in the rabbit nerve and as small as 6/jtfjtm 2 in the garfish nerve.

Rate of action ofAnemonia sulcata toxin II on sodium channels in myelinated nerve fibres

1982 ◽  
Vol 394 (4) ◽  
pp. 313-319 ◽  
Author(s):  
Johann Schmidtmayer ◽  
Mechthild Stoye-Herzog ◽  
Werner Ulbricht
Keyword(s):  
Sodium Channels ◽  
Nerve Fibres ◽  
Myelinated Nerve

Sodium and potassium channels in regenerating and developing mammalian myelinated nerves

1982 ◽  
Vol 215 (1200) ◽  
pp. 273-287 ◽  
Keyword(s):  
Potassium Channels ◽  
Action Potential ◽  
Sodium Channels ◽  
Unit Length ◽  
Nerve Fibres ◽  
Myelinated Nerve ◽  
Complementary Distribution ◽  
Myelinated Nerves ◽  
Sodium And Potassium ◽  
Regenerating Nerve

A study has been made of how the normal complementary distribution of sodium and potassium channels in mammalian myelinated nerve fibres (all the sodium channels being in the node with all the potassium channels in the internode) is altered in regenerating and in developing rabbit sciatic nerves. In regenerating nerve fibres, where a marked increase in the number of nodes per unit length occurs, there is a corresponding increase in the sodium channel content (determined from the maximum saturable binding of labelled saxitoxin), consistent with the idea that the number of sodium channels per node remains roughly constant. The use of 4-aminopyridine, which by blocking potassium channels prolongs the action potential, has shown that both in regenerating nerve fibres and in developing nerve fibres potassium currents contribute to the mammalian action potential. In both cases, with the passage of time, the sensitivity to 4-aminopyridine progressively decreases.

scholarly journals Mediation of Elicitin Activity on Tobacco Is Assumed by Elicitin-Sterol Complexes

2001 ◽  
Vol 12 (9) ◽  
pp. 2825-2834 ◽  
Author(s):  
Hanan Osman ◽  
Sébastien Vauthrin ◽  
Vladimir Mikes ◽  
Marie-Louise Milat ◽  
Franck Panabières ◽  
...  
Keyword(s):  
Binding Sites ◽  
Defense Mechanisms ◽  
Specific Binding ◽  
Biological Effects ◽  
Chemical Characterization ◽  
Site Directed Mutagenesis ◽  
Specific Binding Sites ◽  
Biological Responses ◽  
Kinetics Of

Elicitins secreted by phytopathogenic Phytophthoraspp. are proteinaceous elicitors of plant defense mechanisms and were demonstrated to load, carry, and transfer sterols between membranes. The link between elicitor and sterol-loading properties was assessed with the use of site-directed mutagenesis of the 47 and 87 cryptogein tyrosine residues, postulated to be involved in sterol binding. Mutated cryptogeins were tested for their ability to load sterols, bind to plasma membrane putative receptors, and trigger biological responses. For each mutated elicitin, the chemical characterization of the corresponding complexes with stigmasterol (1:1 stoichiometry) demonstrated their full functionality. However, these proteins were strongly altered in their sterol-loading efficiency, specific binding to high-affinity sites, and activities on tobacco cells. Ligand replacement experiments strongly suggest that the formation of a sterol-elicitin complex is a requisite step before elicitins fasten to specific binding sites. This was confirmed with the use of two sterol-preloaded elicitins. Both more rapidly displaced labeled cryptogein from its specific binding sites than the unloaded proteins. Moreover, the binding kinetics of elicitins are related to their biological effects, which constitutes the first evidence that binding sites could be the biological receptors. The first event involved in elicitin-mediated cell responses is proposed to be the protein loading with a sterol molecule.

Olfactory and Chemical Characterization of Indoor Air-Towards a Psychophysical Model for Air Quality

1981 ◽  
Author(s):  
Birgitta Berglund ◽  
Ulf Berglund ◽  
Thomas Lindvall ◽  
Helene Nicander-Bredberg
Keyword(s):  
Air Quality ◽  
Indoor Air ◽  
Chemical Characterization

PURIFICATION AND PARTIAL CHEMICAL CHARACTERIZATION OF SHEEP NEUROPHYSIN

1973 ◽  
Vol 74 (2) ◽  
pp. 226-236 ◽  
Author(s):  
Michel Chrétien ◽  
Claude Gilardeau
Keyword(s):  
Amino Acid ◽  
Polyacrylamide Gel Electrophoresis ◽  
Chemical Characterization ◽  
Terminal Amino Acid ◽  
Amino Acid Determination ◽  
Pituitary Glands ◽  
Terminal Amino ◽  
Partial Chemical ◽  
Acid Determination

ABSTRACT A protein isolated from ovine pituitary glands has been purified, and its homogeneity assessed by NH2- and COOH-terminal amino acid determination, ultracentrifugation studies, and polyacrylamide gel electrophoresis after carboxymethylation. Its chemical and immunochemical properties are closely similar to those of beef and pork neurophysins, less similar to those of human neurophysins. It contains no tryptophan (like other neurophysins) or histidine (like all except bovine neurophysin-I and human neurophysins). It has alanine at the NH2-terminus and valine at the COOH-terminus. Its amino acid composition is similar to, but not identical with those of porcine and bovine neurophysins.

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