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Showing papers on "Polyamine binding published in 1998"


Journal ArticleDOI
TL;DR: The interaction of spermine with both ifenprodil and the related NR2B selective antagonist Ro 8–4304 at the NMDA receptor in rat cultured cortical neurones in the presence of saturating concentrations of glycine was studied, supporting the suggestion that Mg2+ might be the physiological ligand acting at the sPermine site mediating glycine‐independent stimulation.
Abstract: 1The atypical NR2B subunit-selective NMDA receptor antagonist ifenprodil was originally believed to act as a competitive antagonist at the polyamine binding site of the NMDA receptor. However, a number of studies have suggested that ifenprodil might bind to a distinct site. 2Using whole-cell voltage clamp recordings, we have studied the interaction of spermine with both ifenprodil and the related NR2B selective antagonist Ro 8–4304 at the NMDA receptor in rat cultured cortical neurones in the presence of saturating concentrations of glycine. 3Ifenprodil and Ro 8-4304 inhibited steady-state currents evoked by 100 μm NMDA in the absence of spermine with IC50 values of 0.3 and 0.6 μm, respectively. In the presence of 1 and 3 mm spermine, IC50 values for ifenprodil were 1.4 and 1.8 μm and for Ro 8-4304 they were 3.0 and 7.5 μm, respectively. 4In the presence of spermine, the on-time constant of receptor blockade by both antagonists was significantly slower than control and the off-time constant of recovery from receptor blockade following removal of Ro 8-4304 was significantly faster. 5Fast application of spermine during an NMDA steady-state current in the continuous presence of a subsaturating concentration of either antagonist resulted in a biphasic increase in the current, consistent with a fast increase upon spermine binding and a slow increase resultant from dissociation of antagonist due to spermine binding-induced allosteric reduction in receptor antagonist affinity. In agreement with this, at higher, saturating concentrations of antagonist, the slow increase in current amplitude was markedly reduced or absent. 6These observations are consistent with a non-competitive, allosteric interaction between spermine and the antagonists, such that spermine binding to the NMDA receptor results in a reduction in receptor affinity for the antagonists and vice versa. 7The effects of Mg2+ on the NMDA-evoked currents and its interaction with ifenprodil were similar to those of spermine, supporting the suggestion that Mg2+ might be the physiological ligand acting at the spermine site mediating glycine-independent stimulation.

80 citations


Journal ArticleDOI
TL;DR: In this work, spermidine binding to total proteins solubilized from plasma membrane purified from zucchini (Cucurbita pepo L.) hypocotyls was investigated and partial purification on Sephadex G-200 led to the identification of 66- and 44-kD protein bands, which may represent the putative sperMidine-binding protein(s) on the plasmalemma.
Abstract: In this work [14C]spermidine binding to total proteins solubilized from plasma membrane purified from zucchini (Cucurbita pepo L.) hypocotyls was investigated. Proteins were solubilized using octyl glucoside as a detergent. Specific polyamine binding was thermolabile, reversible, pH dependent with an optimum at pH 8.0, and had a Kd value of 5 μm, as determined by glass-fiber-filter assays. Sephadex G-25 M gel-filtration assays confirmed the presence of a spermidine-protein(s) complex with a specific binding activity. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis and native polyacrylamide gel electrophoresis of collected fractions having the highest specific spermidine-binding activity, several protein bands (113, 75, 66, and 44 kD) were identified. The specificity of spermidine binding was examined by gel-filtration competition experiments performed using other polyamines and compounds structurally related to spermidine. Partial purification on Sephadex G-200 led to the identification of 66- and 44-kD protein bands, which may represent the putative spermidine-binding protein(s) on the plasmalemma.

57 citations


Journal ArticleDOI
TL;DR: Results are consistent with the existence of two polyamine binding sites associated with the NMDA receptor complex, one of the sites appears to preferentially recognize lipophilic substances while the other favors hydrophilic materials.
Abstract: The effect of 1,3-diamines on basal and spermine-stimulated [3H]MK-801 binding was investigated. Systematic variations in the molecular parameters revealed that, in general, lipophilic 1,3-diamines inhibited and hydrophilic 1,3-diamines enhanced [3H]MK-801 binding in the nominal absence of glutamate and glycine. Furthermore, 1,3-diamines which were highly monoprotonated at physiologic pH were more effective in modulating basal binding (at 100 μM 1,3-diamine) than analogues which were mostly diprotonated or unprotonated. Finally, the internuclear distance between the amino nitrogens and the extent of modulation of basal [3H]MK-801 binding were correlated. Similar, but more modest, effects were seen for spermine-enhanced [3H]MK-801 binding. These results are consistent with the existence of two polyamine binding sites associated with the NMDA receptor complex. One of the sites appears to preferentially recognize lipophilic substances while the other favors hydrophilic materials. Both sites appear to recogni...

47 citations


Journal ArticleDOI
TL;DR: Thermodynamic analysis of spermine binding to mitochondria treated with ruthenium red and deenergized with either FCCP or antimycin A confirms the presence of two polyamine binding sites, S1 and S2, both with monocoordination, as previously observed in energized mitochondria.

13 citations


Journal ArticleDOI
TL;DR: The present study aimed to characterize the effects in mice of another NMDA receptor antagonist acting at polyamine binding site, eliprodil, to find out whether group-housed and individually housed nonstressed mice are more likely to be affected by housing/stressing or drug exposures during the conditioning period.

9 citations


Journal ArticleDOI
TL;DR: The intestinal brush-border membrane may contain at least three sites specific for polyamine binding and exhibiting different ligand selectivity, which might be associated with the transport system already described for intestinal uptake of PUT.

7 citations


01 Jan 1998
TL;DR: The most promising compounds that have potentials as anticonvulsants are partial and competitive antagonists of the glycine binding site and competitive antagonist of the polyamine binding sites as discussed by the authors.
Abstract: NMDA is the excitatory amino acid receptor subtype that is most thoroughly studied It is an ionotropic receptor with Mg 2+ blockage in a voltage-dependent manner Functional NMDA receptor consists of a heterodimer of NMDAR1 and NMDAR2 subunits Alternative splicing of the products of exons 5, 21 and 22 results in 7 naturally occuring isoforms lmpotant allosteric binding sites on the NMDA receptors are Zn 2+ , glycine and polyamine binding sites Since the competitive NMDA antagonists and the noncompetitive antagonists are mostly associated with psychotomimetic effects, attention has recently been paid toward the development of ligands that bind to the glycine and polyamine binding sites The most promising compounds that have potentials as anticonvulsants are partial and competitive antagonists of the glycine binding site and competitive antagonists of the polyamine bindings sites