THE STRUCTURAL ANALYSIS OF PHOTO-TRANSDUCTION PROTEINS

这项国际合作研究的目的是与Wayne州立大学Kresge眼科研究所的Akio Yamazaki博士合作，揭示脊椎动物光感受器细胞中光转导过程的形态学对应物。1998年，我们研究了光转导的关键成分之一磷酸二酯酶（PDE）的形态变化以及PDE亚基的功能变化，并阐明了PDE在视觉信号转导机制中的新作用。与对光导信号流和各组分在信号流中的作用的理解取得重大进展相反，由于完整的Pαβ的纯化和表达困难以及缺乏关于Pαβ- p γ相互作用调控的信息，PDE亚基之间的关系尚不清楚。然而，在本研究中，Pαβ-Pγ的相互作用被部分阐明，Pγ修饰机制的新发现和PDE在杆外段细胞质cGMP水平升高中的作用的意外发现。我们最近在牛Pαβ的分离纯化和不含Pγ方面的进展也使得在电子显微镜下观察分子成为可能。所有类型的PDE （αβγγ, αβγ, αβ）基本上都是由两条弯曲的具有特征形状的链组成，它们排列成一个环。完全PDE中由Pγ位错引起的结构变化被捕获为分子位置的三维位移。1999年，我们开始研究突触带的功能结构，突触带位于活性位点，被突触囊泡晕包围。我们的新电子显微镜显示突触带与Ca有关。由于突触带在电子能量损失光谱成像中代表了丰富的磷元素信号，很明显突触带是膜的衍生物。

The aim of this international cooperative research with Dr Akio Yamazaki, Kresge Eye Institute, Wayne State University, was to reveal morphological counterpart of the photo-transduction process in the vertebrate photoreceptor cells. In 1998, we have investigated morphological change of phosphodiesterase (PDE), one of the key components in phototransduction, accompanied by functional changes in PDE subunits and to elucidate new roles of PDE in visual signal transduction mechanism. In contrast to significant progress in understanding the flow of signals in phototransduction and the roles of each component in the flow of signals, the relationship in PDE subunits is unknown because of difficulty of purification and expression of intact Pαβ and lack of information about regulation of Pαβ-Pγinteractions. However, in this study, Pαβ-Pγ interactions were partially elucidated with new findings on the mechanism of Pγ modifications and unexpected finding on the PDE role in the increase of cytoplasmic cGMP level in rod outer segments. Our recent development in the isolation and purification of bovine Pαβ with or without Pγ also made possible to observe the molecules under electron microscope. All types of PDE (αβγγ, αβγ, αβ) consisted basically of two crooked strands with characteristic shape that were arranged as making a ring. Suggestible structural changes induced by dislocation of Pγ from complete PDE were arrested as three dimensional shift of molecules in position. In 1999, we started to study the functional structure of synaptic ribbons that are located at the active site and surrounded by a halo of synaptic vesicles. Our new electron microscopy revealed surprisingly that synaptic ribbon was associated with Ca. Since synaptic ribbon represented abundant phosphorus element signals in electron energy loss spectral imaging, it is clear that the synaptic ribbon is a derivative of the membrane.