跨膜Ca^（2＋）梯差通过调节膜脂流动性影响G_s激活腺苷酸环化酶

将牛脑皮层激活型Ｇ－蛋白（Ｇｓ）和腺苷酸环化酶（ＡＣ）重建于大豆磷脂脂质体，形成具有或不具有１０００倍跨膜Ｃａ２＋梯差的四种脂酶体，研究了跨膜Ｃａ２＋梯差对Ｇｓ功能的影响及其与膜脂物理状态的关系。结果表明，在具有与生理条件相似的正向跨膜Ｃａ２＋梯差的脂酶体Ａ中，ＡＣ的基础活力和Ｇｓ对ＡＣ的激活活力均最大；而跨膜Ｃａ２＋梯差与生理条件相反时（脂酶体Ｄ），ＡＣ的基础活力和Ｇｓ对ＡＣ的激活作用最小。外加Ｃａ２＋载体Ａ２３１８７消除脂酶体两侧的Ｃａ２＋梯差可导致前者（脂酶体Ａ）Ｇｓ功能降低和后者（脂酶体Ｄ）Ｇｓ功能增强，使两者Ｇｓ功能恢复到无跨膜Ｃａ２＋梯差的脂酶体水平。用荧光探针ＤＰＨ标记上述四种大豆磷脂制备的磷酶体，以时间分辨纳秒荧光技术研究在不同跨膜Ｃａ２＋梯差条件下膜脂物理状态变化。四种脂酶体的荧光各向异性测量结果表明，具有正向跨膜Ｃａ２＋梯差的脂酶体Ａ的序参数（Ｓ＝０．３２８），微粘度（η＝０．６１ｐ）和旋转相关时间（τｒ＝２．４ｎｓｅｃ）均较具有反向Ｃａ２＋梯差的脂酶体Ｄ者（Ｓ＝０．３５２，η＝０．６４ｐτｒ＝２．５ｎｓｅｃ）小，即前者的膜脂流动性较后者增加。这可能提示，一个相似于生理条件的跨膜Ｃａ２＋?

Reconstitution of Gs and Adenylate Cyclase From Bovine Brain Cortices on Asolectin Liposomes

Signal transduction across cell membranes is an important subject of the current studies on biomembranes. Hormonally regulated adenylate cyclase signalling system is composed of three distinct types of plasma-membrane associated proteins: the receptor, adenylate cyclase (AC) and stimulatory GTP-binding protein (Gs) which me-

Purification of β-adrenergic receptors from Beijing duck erythrocyte plasma membranes and their reconstitution with Gs and adenylate cyclase on asolectin liposomes

Catecholamines such as adrenaline, norepinephrine and isoproterenol regulate a wide variety of physiological responses via their specific binding to adrenergic receptors located in the plasma membrane. Adrenergic receptors have been divided into two major types, α and β. Binding of ligands to β-adrenergic receptors (β-AR) first triggers the activation of stimulatory GTP-binding protein (Gs). The activated Gs then interacts