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Abstract: [3 H]Kainate bound to chick cerebellar membranes with a K D of 0.6 μ M and with an exceptionally high B max of 165 pmol/mg of protein. In octylglucoside-solubilised extracts, the affinity of [3 H]kainate was reduced ( K D = 2.7 μ M ), but the B max was relatively unchanged (130 pmol/mg of protein). The rank potency of competitive ligands was domoate > kainate > 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) > glutamate. Binding sites for α-[3 H]amino-3-hydroxy-5-methylisoxazolepropionate ([3 H]AMPA) were much less abundant, with K D and B max values in membranes of 86 n M and I pmol/mg of protein, respectively. The affinity of [3 H]AMPA binding was also reduced on solubilisation ( K D = 465 n M ), but there was an increase in the B max (1.7 pmol/mg of protein). Quisqualate and CNQX were the most effective displacers of [3 H]AMPA binding, but kainate was also a relatively potent inhibitor. However, in contrast to the displacement profile for [3 H]kainate, domoate was markedly less potent than kainate at displacing [3 H]AMPA. These results suggest that [3 H]AMPA binds to a small subset of the kainate sites that, unlike the majority of the [3 H]kainate binding protein, which has been reported to be located in the Bergmann glia, may represent neuronal unitary non- N -methyl-D-aspartate receptors. 相似文献
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The chlorophyll-protein complexes of Acetabularia. A novel chlorophyll complex which forms oligomers
(1) Five minor chlorophyll-protein complexes were isolated from thylakoid membranes of the green alga Acetabularia by SDS-polyacrylamide gel electrophoresis, after SDS or octylglucoside solubilization. None of them were related to CP I (Photosystem I reaction center core) or CP II (chlorophyll light-harvesting complex). (2) Two complexes (CPa-1 and CPa-2) contained only chlorophyll (Chl) a, with absorption maxima of 673 and 671 nm, and fluorescence emission maxima of 683 nm compared to 676 nm for CP II. The complexes had apparent molecular masses of 43–47 and 38–40 kDa, and contained a single polypeptide of 41 and 37 kDa, respectively. They each account for about 3% of the total chlorophyll. (3) Three complexes had identical spectra, with Chl ratios of 3–4 compared to 2 for thylakoid membranes, and a pronounced shoulder around 485 nm indicating enrichment in carotenoids. One of them was the complex ‘CP 29’ (Camm, E.L. and Green, B.R. (1980) Plant Physiol. 66, 428–432) and the other two were slightly different oligomeric forms of CP 29. They could be formed from CP 29 during reelectrophoresis; but about half the complex was isolated originally in an oligomeric form. Together they account for at least 7% of the total chlorophyll. Their function is unknown. 相似文献
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Reelectrophoresis of the oligomer form (CP II1) of the chlorophyll light-harvesting complex (LHC) from the green alga Acetabularia yields two green bands which run at the position typical of the monomer (CP II). The upper green band (CP II1) is enriched in the 27 kDa polypeptide of the LHC, while the lower is enriched in the 26 kDa polypeptide. The fact that both bands have both chlorophyll (Chl) a and b, and in the same ratio, implies that the LHC is made up of two Chl proteins. Neither of these bands can be attributed to the Chl complex ‘CP 29’ (Camm, E.L. and Green, B.R. (1980) Plant Physiol. 66, 428–432). Resolution of CP II1 and CP II2 of spinach can be obtained if sucrose gradient fractions of an octylglucoside extract are subjected to SDS-polyacrylamide gel electrophoresis. CP II1 and CP II2 are interpreted as being fundamental subunits of the light-harvesting complex as it is defined on SDS-polyacrylamide gels. 相似文献
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The structural preferences of mixed lipid systems containing egg yolk or phosphatidylethanolamine and representative detergents (Triton X-100, deoxycholate, octylglucoside and lyso-phosphatidylcholine) have been examined. It is shown that all these detergents exhibit an ability to stabilize a bilayer organization for the phosphatidylethanolamine at detergent to phosphatidylethanolamine molar ratios of 0.05 to 0.5, depending on the detergent and/or phosphatidylethanolamine species. These results are interpreted in terms of molecular shape, where the ‘inverted cone’ shape detergents combine in a complementary fashion with ‘cone shaped’ phosphatidylethanolamine to result in net bilayer structure. 相似文献
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We have investigated the stability of giant unilamellar vesicles (GUVs) and large unilamellar vesicles (LUVs) of lipid membranes in the liquid-ordered phase (lo phase) against a detergent, Triton X-100. We found that in the presence of high concentrations of Triton X-100, the structure of GUVs and LUVs of dipalmitoyl-PC (DPPC)/cholesterol (chol) and sphingomyelin (SM)/chol membranes in the lo phase was stable and no leakage of fluorescent probes from the vesicles occurred. We also found that ether-linked dihexadecylphosphatidylcholine (DHPC) membranes containing more than 20 mol% cholesterol were in the lo phase, and that DHPC/chol-GUV and DHPC/chol-LUV in the lo phase were stable and no leakage of internal contents occurred in the presence of Triton X-100. In contrast, octylglucoside solution could easily break these GUVs and LUVs of the lo phase membranes and induced internal contents leakage. These data indicate that GUVs and LUVs of the lo phase membranes are very valuable for practical use. 相似文献
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(1) Octylglucoside stimulates an Mg2+-specific ATPase activity with CF1 preparations from different higher plants and the alga Chlamydomonas reinhardii. (2) Tentoxin at high concentrations (10?4–10?3 M) in the presence of octylglucoside further stimulates the Mg2+-ATPase activity of CF1 from tentoxin-sensitive species and inhibits the activity of CF1 from tentoxin-resistant species. The extent of tentoxin stimulation and inhibition varies among species. A maximal stimulation of over 2-fold was obtained with spinach CF1 and a maximal inhibition of 50% was obtained with C. reinhardii CF1. In Nicotiana spp., tentoxin had only a marginal effect on the Mg2+-ATPase activity induced by octylglucoside. 相似文献
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