Structural biology of calcium channels

***所有活细胞都被一层由油性脂质构成的屏障所包围，这种屏障保护细胞内容物的完整性，并将它们与环境中不受控制的变化隔离开来。然而脂溶性膜限制了大分子以及带负电和正电的小分子（离子）的交换或转移，而这些分子是细胞进行各种活动（包括生长和繁殖）所需要的。生命需要细胞外和细胞内介质的不断交换。特别是，快速的生物反应源于离子的通过，这是由称为“离子通道”的特殊膜蛋白形成的水孔所催化的。电压门控钙离子通道是执行重要生物任务的离子通道之一。这种纳米机器经过优化，可以专门在细胞中携带钙离子，而且必须在严格的限制下进行，因为过多或过少的钙对细胞都是致命的。这种狭窄的操作范围可以部分解释这个离子通道的复杂性，实际上是由多个蛋白质在一个大分子复合物中紧密相互作用组成的。这些辅助蛋白或亚基调节离子的流动。其中一些蛋白质增加了离子的流量，而另一些则减少了通过离子通道的离子的数量。我们长期以来的目标是阐明每一种辅助蛋白的性质以及它们在离子通道复合体内相互作用的性质。为了实现这一目标，我们多年来在结构生物学、生物化学和生物物理学中开发了特定的工具来研究这些蛋白质。我实验室的研究使用精确的电记录技术来研究钙的运动，当它们通过钙通道并穿过细胞膜时。我们还将钙离子的运动与这些蛋白质的初级和三维结构的变化联系起来。尽管这些蛋白质中的大多数已经被发现了20多年，但去年在这些蛋白质的结构生物学方面的最新进展揭示了一种相对未知的蛋白质，称为伽马亚基，它可能在骨骼肌的功能中起决定性作用。因此，拟议的研究旨在了解骨骼肌中蛋白质与钙通道相互作用的性质和特异性，以便更好地了解伽马亚基如何通过细胞膜调节钙通量。拟议的研究将最终提供组织特异性蛋白质网络的结构基础，负责通过细胞膜传导钙离子。

***All living cells are surrounded by a barrier made out of oily lipids that serves to protect the integrity of the cell contents and isolate them from uncontrolled variations from the environment. The liposoluble membrane however limits the exchange or transfer of large molecules as well as small negatively and positively charged molecules (ions) which are needed by the cell for various activities including growth and reproduction. Life requires constant exchange between the extracellular and the intracellular media. In particular, fast biological responses result from the passage of ions that is catalyzed by the presence of aqueous pores that are formed by specialized membrane proteins called “ion channels”. The voltage-gated calcium channel is one of those ion channels that perform an essential biological task. This nanomachine is optimized to specifically carry calcium ions in the cell and must do so within strict limits because too much or too little calcium is lethal to the cell. This narrow range of operation could account in part for the complexity of this ion channel that is in fact made of multiple proteins interacting tightly within a macromolecular complex. These auxiliary proteins or subunits regulate the flow of ions. Some of these proteins increase the flow and some decrease the amount of ions going through the ion channel. It has been our long time goal of elucidate the nature of each of these auxiliary proteins and the nature of their interaction within the ion channel complex. To reach this goal, we have developed over the years specific tools in structural biology, biochemistry and biophysics to study these proteins. Research in my lab uses precise electrical recording techniques to study the movement of calcium, as they move through the calcium channel and across the cell membrane. We are also correlating the movement of calcium ions with changes in the primary and tri-dimensional structure of these proteins. Although most of these proteins have been known for more than 20 years, recent advances in the structural biology of these proteins last year have revealed a relatively unknown protein called the gamma subunit that may play a determinant role in the function of the skeletal muscle. The proposed research is thus aimed at understanding the nature and the specificity of the protein -protein interactions with the calcium channel in the skeletal muscle in order to better understand how this gamma subunit modulates calcium fluxes through the cell membrane. The proposed research will ultimately provide the structural basis underlying the tissue-specific protein networks responsible to conduct calcium ions through the cell membrane.