NMR STUDIES OF C2 DOMAINS OF SYNAPTOTAGMIN I

突触结合蛋白参与Ca ~（2+）诱导的神经传递 release. 突触结合蛋白大致有4个结构域：囊泡内 结构域、跨膜结构域和2个胞质结构域。 两种胞质 域被命名为C2 A和C2B。 第一个域是要研究的域 通过核磁共振。 已知C2 A结构域是膜中的Ca 2+传感器 胞吐作用 根据在存在下的Ca 2+结合测定， 磷脂，希尔系数大于3，这反过来 意味着C2 A应结合至少3个Ca 2+离子。 到目前为止，X光 结构发现一个Ca 2+结合位点，NMR数据表明 第二个网站。 最近，X射线结构的PLC-？1的 具有C2结构域，基于同源性提出第三结合位点 这两个结构。 未能找到第三个结合位点 推测是由于脂质的缺乏， C2 A结构域对Ca 2+固有亲和力低。 在当前的NMR 对这种C2 A结构域的研究， 采用 NMR数据显示化学位移随着 Ca 2+或脂质或两者，这强烈表明存在一个 三元络合物 本研究的目的是解决结构的 三元复合物：C2 A-Ca ~（2+）-类脂。

The synaptotagmin is involved in the Ca2+-induced neurotrasmitter release. The synaptotagmin has roughly 4 domains: intravesicular domain, transmembrane domain, and 2 cytosolic domains. Two cytosolic domains are named C2A and C2B. The first domain is the one to study by NMR. C2A domain is known to be a Ca2+ sensor in the membrane exocytosis. According to the Ca2+ binding assay in the presence of phospholipids, the Hill coefficient is larger than 3, which in turn means C2A should bind at least 3 Ca2+ ions. So far, the x-ray structure found one Ca2+ binding site, and NMR data suggested the second site. Very recently, the x-ray structure of the PLC-?1 which has a C2 domain proposed the third binding site based on the homology of the two structures. The failure in finding the third binding site is presumed to result from the absence of the lipids since the intrinsic affinity of C2A domain to Ca2+ is low. In the current NMR study of this C2A domain, a short version of the phospholipid has been used. NMR data show changes in the chemical shifts with the presence of Ca2+ or lipid or both, which strongly suggests a existence of a ternary complex. The goal of this study is to solve the structure of the ternary complex: C2A-Ca2+-lipid.