STRUCTURAL BIOLOGY AND SIGNAL TRANSDUCTION

磷脂酰肌醇激酶在信号转导中起重要作用 通过在特定的磷酸化肌醇环转导 岗位IIb型酶的结构 磷脂酰肌醇磷酸激酶，揭示了一种蛋白激酶 ATP结合核心，并证明所有磷酸肌醇 激酶属于一个超家族。这种酶是一种圆盘状的 具有33 × 48 A基本平面的同二聚体，表明 用于质膜靶向的静电机制。保守 碱性残基形成假定的磷脂酰肌醇磷酸 特异性位点底物结合位点在一侧是开放的， 与磷脂酰肌醇3-和 5-磷酸盐。具有膜结合基质的模拟复合物 ATP显示磷酸肌醇激酶如何磷酸化 在膜界面处的原位基质。 去年，我们 确定了腺苷酸环化酶核心的结构，并显示 它由一对排列成花环的催化域组成。 同型半胱氨酸催化结构域排列在不同的腺苷酰和 对称同型二聚体或假对称的鸟苷酸环化酶 异二聚体。我们证实了腺苷酸和 鸟苷酸环化酶通过将光感受器鸟苷酸环化酶转化为 腺苷酸环化酶。我们还使用定点突变来 探讨表明Asp-310在催化金属离子中的作用 I型腺苷酸环化酶机制中的结合。整体 腺苷酸和鸟苷酸环化酶机制的图片，催化是 当一个结构域上的两个金属结合Asp残基被 另一个是关键的Asn/Arg对。变构 哺乳动物腺苷酸环化酶激活剂，毛喉素和Gsa， 促进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.