STRUCTURAL BIOLOGY AND SIGNAL TRANSDUCTION

磷脂酰肌醇激酶在信号转导中的核心作用 特异性磷酸化肌醇环的转导 各就各位。IIb型这种酶的一种结构 磷脂酰肌醇磷酸激酶，揭示一种蛋白激酶 ATP结合核心，并证明所有的磷脂酰肌醇 蛋白激酶属于一个超家族。该酶为圆盘状。 具有33 x 48 A基本平面的同源二聚体，表明 质膜靶向的静电机理。保守的 碱性残基形成假定的磷脂酰肌醇磷酸 特异性部位。底物结合部位一侧开放， 与磷脂酰肌醇3-和磷脂酰肌醇的双重特异性一致 5-磷酸盐。一种膜结合底物的模拟络合物 而三磷酸腺苷展示了肌醇磷脂激酶是如何磷酸化的。 它的底物在膜界面原位。在前一年，我们 确定了腺酰环化酶核心的结构，并显示 它由一对排成花环的催化域组成。 同源催化结构域排列在不同的腺苷和 鸟苷酸环酶作为对称的同源二聚体或假对称 杂二聚体。我们确认了腺苷的亲缘关系 光感受器鸟酰环化酶转化为鸟苷酸环化酶 一种腺苷酸环化酶。我们还使用了定点突变技术来 探索演示Asp-310在催化金属离子中的作用 I型腺酰环化酶的结合机制。总体而言 图为腺基和鸟苷酸环化酶的机理，催化是 当一个结构域上的两个金属结合天冬氨酸残基被激活时 与另一台上的密钥ASN/Arg对并置。变构 哺乳动物腺酰环化酶激活剂，Forsklin和GSA， 促进这两个结构域的催化最佳并置。

Phosphoinositide kinases play central roles in signal transduction by phosphorylating the inositol ring at specific positions. The structure of one such enzyme, type IIb phosphatidylinositol phosphate kinase, reveals a protein kinase ATP-binding core and demonstrates that all phosphoinositide kinases belong to one superfamily. The enzyme is a disc-shaped homodimer with a 33 x 48 A basic flat face that suggests an electrostatic mechanism for plasma membrane targeting. Conserved basic residues form a putative phosphatidylinositol phosphate specificity site. The substrate binding site is open on one side, consistent with dual specificity for phosphatidylinositol 3- and 5-phosphates. A modeled complex with membrane-bound substrate and ATP shows how a phosphoinositide kinase can phosphorylate its substrate in situ at the membrane interface. In the prior year we determined the structure of the adenylyl cyclase core and showed that it consists of a pair of catalytic domains arranged in a wreath. Homologous catalytic domains are arranged in diverse adenylyl and guanylyl cyclases as symmetric homodimers or pseudosymmetric heterodimers. We confirmed the kinship of the adenylyl and guanylyl cyclases by converting photoreceptor guanylyl cyclase into an adenylyl cyclase. We also used site-directed mutagenesis to explore demonstrate the role of Asp-310 in catalytic metal ion binding in the mechanism of type I adenylyl cyclase. In the overall picture of the adenylyl and guanylyl cyclase mechanism, catalysis is activated when two metal-binding Asp residues on one domain are juxtaposed with a key Asn/Arg pair on the other. Allosteric activators of mammalian adenylyl cyclase, forskolin and Gsa, promote the catalytically optimal juxtaposition of the two domains.