Structure-function analysis of phosphatidylinositol transfer protein alpha bound to human phosphatidylinositol
Structure-function analysis of phosphatidylinositol transfer protein alpha bound to human phosphatidylinositol
复制标题
DOI：
10.1016/j.str.2004.01.013
复制
发表时间：
2004-02-01
期刊：
影响因子：
5.7
通讯作者：
McDonald, NQ
中科院分区：
文献类型：
--
作者：
Tilley, SJ;Skippen, A;McDonald, NQ
磷脂酰肌醇转移蛋白α（PITPalpha）选择性转运并促进脂质双层之间磷脂酰肌醇（PI）和磷脂酰胆碱（PC）的交换。在高等真核生物中，PITPalpha是细胞功能所必需的，如磷脂酶C介导的信号传导，调节胞吐作用和分泌囊泡形成。我们已经以2.95埃的分辨率确定了与其生理配体PI结合的人PITPalpha的晶体结构。该结构确定了脂质头基结合口袋内的关键侧链，这些侧链定义了PI的精确特异性。PI结合口袋的突变分析与结构数据非常一致，并允许操纵PITPalpha的功能特性。令人惊讶的是，有没有主要的构象之间的差异PI-和PC-加载PITPalpha，尽管以前的预测。在晶体中，PITPalpha-PI是二聚体，在不对称单元中具有两个相同的二聚体。二聚体界面精确地掩盖了我们确定为有助于PITPa膜相互作用的序列。我们的结构代表了一个可溶性的，运输能力形式的PI负载PITPalpha。
Phosphatidylinositol transfer protein alpha (PITPalpha) selectively transports and promotes exchange of phosphatidylinositol (PI) and phosphatidylcholine (PC) between lipid bilayers. In higher eukaryotes PITPalpha is required for cellular functions such as phospholipase C-mediated signaling, regulated exocytosis, and secretory vesicle formation. We have determined the crystal structure of human PITPalpha bound to its physiological ligand, PI, at 2.95 Angstrom resolution. The structure identifies the critical side chains within the lipid-headgroup binding pocket that define the exquisite specificity for PI. Mutational analysis of the PI binding pocket is in good agreement with the structural data and allows manipulation of functional properties of PITPalpha. Surprisingly, there are no major conformational differences between PI- and PC-loaded PITPalpha, despite previous predictions. In the crystal, PITPalpha-PI is dimeric, with two identical dimers in the asymmetric unit. The dimer interface masks precisely the sequence we identify as contributing to PITPa membrane interaction. Our structure represents a soluble, transport-competent form of PI-loaded PITPalpha.