【摘要】 文中报导了本实验室最近发现的一种新型钙调蛋白（CaM）天然拮抗剂——酸枣仁皂甙A,它能显著地抑制CaM活化PDE的活力.为研究它与CaM间的相互作用,本实验还制备了与天然CaM具有相同激活PDE能力的丹磺酰钙调蛋白（D-CaM）.D-CaM的荧光光谱研究表明,酸枣仁甙A的加入诱导CaM分子的疏水位点更加暴露,从而增强丹磺酰基团的荧光发射量子产率.桔抗剂与CaM间的结合是绝对依赖Ca²⁺的.荧光滴定的结果证明此结合的解离常数为2.8μM.酸枣仁皂甙A能进一步加强三氟啦嗪（TFP）所诱导的D-CaM荧光增强.这结果暗示,它不与TFP竞l争CaM上相同的结合位点.更多还原

【Abstract】 Jujuboside A is a new natural antagonist of calmodulin. It can efficiently inhibit the calmodulin-activated activity of cyclic nucleotide phosphodieste-rase (PDE) . In order to elucidate its interaction mechanism with calmodulin, we prepared a dansylcalmodulin (D-CaM) which contained approximately 0.6 mol of dansyl per mol calmodulin.The ability of this D-CaM to activated PDE was identical to that of native calmodulin.Study on the fluorescence spectra of D-CaM has shown that upon binding of jujuboside A to calmodulin, the hydrophobic regions of calmodulin can be further exposed, thus the quantum yield of the dansyl bound to calmodulin is increased. The binding of jujuboside A to calmodulin is absolutely Ca2+-depe-ndent. The fluorescence titration showed that calmodulin bound jujuboside A with a Kd value of 2.8 μm.The result that jujuboside A can further enhance the fluorescence increase induced by TFP implies that it doesn’t compete the same binding sites on calmodulin with TFP.更多还原