Kirchhausen T, Toyoda T
Department of Anatomy and Cellular Biology, Harvard Medical School, Boston, Massachusetts 02115.
J Biol Chem. 1993 May 15;268(14):10268-73.
Clathrin is a major component of the basket-like network of hexagons and pentagons that forms the "coat" on the cytoplasmic face of the plasma membrane and the trans Golgi network during the invagination of coated pits. Soluble clathrin is a three-legged structure (triskelion) comprising three identical heavy chains and three different light chains located toward the center of the triskelion on the proximal segment of the leg. All mammalian light chains contain a central domain of 10 heptad repeats, which is necessary for the interaction with heavy chain. Because the repeats are characteristic of alpha helical coiled coils, we proposed that the central domain had an extended conformation (Kirchhausen, T., Scarmato, P., and Harrison, S. C. et al. (1987) Science 236, 320-324). However, an alternative model has recently been proposed (Nathke, I. S., Heuser, J., Lupas, A., Stock, J., Turck, C. W., and Brodsky, F. M. (1992) Cell 68, 899-910). Here, we use single-molecule electron microscopy of clathrin decorated with monoclonal antibodies directed against different epitopes on light chains to show that the light chain central domain has an extended conformation and reaches along most of the proximal segment of the heavy chain leg.
网格蛋白是由六边形和五边形组成的篮状网络的主要成分，在有被小窝内陷过程中，该网络在质膜和反式高尔基体网络的细胞质面上形成“衣被”。可溶性网格蛋白是一种三脚结构（三脚蛋白复合体），由三条相同的重链和三条不同的轻链组成，轻链位于腿部近端朝向三脚蛋白复合体中心的位置。所有哺乳动物的轻链都包含一个由10个七肽重复序列组成的中央结构域，这对于与重链相互作用是必需的。由于这些重复序列是α螺旋卷曲螺旋的特征，我们提出中央结构域具有伸展构象（基尔豪森，T.，斯卡马托，P.，哈里森，S. C.等人（1987年）《科学》236卷，320 - 324页）。然而，最近有人提出了另一种模型（纳特克，I. S.，休泽尔，J.，卢帕斯，A.，斯托克，J.，图尔克，C. W.，布罗德斯基，F. M.（1992年）《细胞》68卷，899 - 910页）。在这里，我们使用针对轻链上不同表位的单克隆抗体修饰的网格蛋白的单分子电子显微镜技术，来表明轻链中央结构域具有伸展构象，并沿着重链腿部的大部分近端延伸。
