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Phytotropins: III. NAPHTHYLPHTHALAMIC ACID BINDING SITES ON MAIZE COLEOPTILE MEMBRANES AS POSSIBLE RECEPTOR SITES FOR PHYTOTROPIN ACTION 下载免费PDF全文
Certain members of the phytotropin class of auxin transport inhibitors are shown to bind with high affinity to the known naphthylphthalamic acid binding sites in maize (Zea mays) coleoptiles. The binding site is, thus, a phytotropin binding site. In general, the degree of binding correlates with the phytotropin structure activity rules and with physiological activities of model compounds. It is argued that the binding site may be a receptor, and it also may be the receptor involved in the control of the auxin transport process. The possibility is raised that the binding sites may be intrinsic receptors for endoanalog(s) of the phytotropins. 相似文献
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本文运用前包埋电镜技术就小麦秆锈菌菌丝体表糖基、抗原位点的测定方法进行了研究。受小麦秆锈菌侵染的小麦叶片经1%戊二醛和4%多聚甲醛固定液先固定后,分别用两个凝集素探针、两个抗体以及A蛋白-胶体金,对样品进行孵育反应,随后样品经2%锇酸后固定、脱水和包埋。电镜下观察到,两个凝集素探针成功地显示出相应的糖基在菌丝体表的分布状况;两个抗体也相应揭示出菌丝体表的抗原位点。结果表明运用该方法来分析测定锈菌体表的化学成分是可行的。 相似文献
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N. H. Yessaian A. R. Armenian E. K. Kazarova H. Ch. Buniatian 《Journal of neurochemistry》1971,18(3):307-321
Abstract— The loss of GABA, norepinephrine and serotonin and the uptake of GABA (in the presence of 1 mM-GABA) and the effect of GABA on the loss of norepinephrine and serotonin were investigated in rat midbrain slices incubated in media of various compositions. In a medium of low Na+ concentration the loss of serotonin from incubated slices was markedly inhibited while that of norepinephrine and GABA was significantly increased. Conversely the most pronounced loss of serotonin from slices was observed on the addition of ouabain to a medium of a balanced ionic composition. Whereas the loss of serotonin from slices increased in a medium of high K+ content, it was significantly reduced after 45 min incubation in a high K+ -low Na+ medium. In all the modified media used, a significant loss of norepinephrine was observed while that of GABA was not affected by the omission of Ca2+ and was slightly reduced in the absence of K+ . GABA enhanced the loss of norepinephrine and inhibited that of serotonin in a high-K+ medium and in one with a balanced ionic composition. A deficiency of Na+ in the medium had a differential effect on the loss of norepinephrine and serotonin similar to that observed with 1 mM-GABA. These results suggest that Na+ may be of crucial importance in the release of serotonin from midbrain slices and that an enhancement of the Na+ extrusion mechanism at the synaptosomal level may be involved in the effect of GABA on brain monoamines. 相似文献
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Ognian C. Ikonomov Diego Sbrissa Homer Fenner Assia Shisheva 《The Journal of biological chemistry》2009,284(51):35794-35806
The phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P2) metabolizing enzymes, the kinase PIKfyve and the phosphatase Sac3, constitute a single multiprotein complex organized by the PIKfyve regulator ArPIKfyve and its ability to homodimerize. We previously established that PIKfyve is activated within the triple PIKfyve-ArPIKfyve-Sac3 (PAS) core. These data assign an atypical function for the phosphatase in PtdIns(3,5)P2 biosynthesis, thus raising the question of whether Sac3 retains its PtdIns(3,5)P2 hydrolyzing activity within the PAS complex. Herein, we address the issue of Sac3 functionality by a combination of biochemical and morphological assays in triple-transfected COS cells using a battery of truncated or point mutants of the three proteins. We identified the Cpn60_TCP1 domain of PIKfyve as a major determinant for associating the ArPIKfyve-Sac3 subcomplex. Neither Sac3 nor PIKfyve enzymatic activities affected the PAS complex formation or stability. Using the well established formation of aberrant cell vacuoles as a sensitive functional measure of localized PtdIns(3,5)P2 reduction, we observed a mitigated vacuolar phenotype by kinase-deficient PIKfyveK1831E if its ArPIKfyve-Sac3 binding region was deleted, suggesting reduced Sac3 access to, and turnover of PtdIns(3,5)P2. In contrast, PIKfyveK1831E, which displays intact ArPIKfyve-Sac3 binding, triggered a more severe vacuolar phenotype if coexpressed with ArPIKfyveWT-Sac3WT but minimal defects when coexpressed with ArPIKfyveWT and phosphatase-deficient Sac3D488A. These data indicate that Sac3 assembled in the PAS regulatory core complex is an active PtdIns(3,5)P2 phosphatase. Based on these and other data, presented herein, we propose a model of domain interactions within the PAS core and their role in regulating the enzymatic activities. 相似文献
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MEMBRANE CHARACTERISTICS AND OSMOTIC BEHAVIOR OF ISOLATED ROD OUTER SEGMENTS 总被引:6,自引:3,他引:6 下载免费PDF全文
Freshly isolated frog rod outer segments are sensitive osmometers which retain their photosensitivity; their osmotic behavior reveals essentially the same light-sensitive Na+ influx observed electrophysiologically in the intact receptor cell. Using appropriate osmotic conditions we have examined freeze-etch replicas of freshly isolated outer segments to identify the membrane which regulates the flow of water and ions. Under isosmotic conditions we find that the disc to disc repeat distance is almost exactly twice the thickness of a disc. This ratio appears to be the same in a variety of vertebrate rod outer segments and can be reliably measured in freeze-etch images. Under all our osmotic conditions the discs appear nearly collapsed. However, when the length of the outer segment is reduced by hyperosmotic shocks the discs move closer together. This markedly reduces the ratio of repeat distance to disc thickness since disc thickness remains essentially constant. Thus, the length reduction of isolated outer segments after hyperosmotic shocks primarily results from reduction of the extradisc volume. Since the discs are free floating and since they undergo negligibly small changes in volume, the plasma membrane alone must be primarily responsible for regulating the water flux and the light-sensitive Na+ influx in freshly isolated outer segments. On this basis we calculate, from the osmotic behavior, that the plasma membrane of frog rod outer segment has a Na+ permeability constant of about 2.8 x 10-6 cm/s and an osmotic permeability coefficient of greater than 2 x 10-3 cm/s. 相似文献
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呼吸链底物和抑制剂对线粒体内膜流动性的影响 总被引:4,自引:0,他引:4
用DPH和ANS标记大鼠肝线粒体内膜,以稳态荧光偏振法,研究了呼吸链底物和抑制剂对内膜流动性的影响。1.苹果酸+谷氨酸、琥珀酸分别为底物,均能引起内膜流动性增加。2.琥珀酸对含心磷脂的脂质体的膜流动性无影响。3.在鱼藤酮存在的条件下,苹果酸+谷氨酸对内膜流动性的增加作用消失,但琥珀酸的作用仍然存在。有氰化钾时则琥珀酸的作用消失。4.不论外加底物存在与否,鱼藤酮使内膜的流动性下降,而氰化钾则使之增加。抗霉素A亦可使内膜的流动性增加。上述结果表明:线粒体内膜流动性与其功能密切相关。电子沿呼吸链传递使线粒体内膜流动性增加,这种变化可能与呼吸链成分的氧化还原态有关。 相似文献
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A number of phospholipids known to be constituents of nerve endings were tested for their ability to inactivate botulinum toxin. Substances tested included phosphatidylcholine, phosphatidalcholine, phosphatidylethanolamine, phosphatidalethanolamine, β-acyl lysolecithin, sphingomyelin, phosphatidylserine, phosphatidic acid, phosphatidylinositol and cardiolipin. Proteolipid from bovine white matter was also tested. Neutral phospholipids potentiated the toxicity in vivo of botulinum toxin, but they had no effect on the toxicity in vitro. Some, but not all, acidic phospholipids caused loss of toxicity of botulinum toxin in solutions at low pH both in vivo and in vitro. However, none of these substances when incubated with toxin under physiological conditions of temperature, pH and ionic strength, caused loss of toxin potency. The data suggest that none of these phospholipids is likely to be a toxin receptor. 相似文献
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EFFECTS OF PHENYL-MERCURIC ACETATE ON STOMATAL AND CUTICULAR RESISTANCE TO TRANSPIRATION 总被引:2,自引:2,他引:0
S. MORESHET 《The New phytologist》1975,75(1):47-52