细胞生物学：第八章 蛋白质分选与膜泡运输.ppt

第一节 细胞内蛋白质的分选 一、信号假说与蛋白质分选信号 二、蛋白质分选转运的基本途径与类型 三、蛋白质向线粒体、叶绿体 和过氧化物酶体的分选 （一） 蛋白质从细胞质基质输入到线粒体 蛋白质从细胞质基质输入到线粒体基质 蛋白质从细胞质基质输入到线粒体线粒体膜间隙、内膜、外膜 * Figure 17-25. Formation of glycosylphosphatidylinositol (GPI)-anchored proteins in the ER membrane. The protein chain is synthesized and initially inserted into the ER membrane as shown in Figure 17-22. A sequence (yellow highlight) in the exoplasmic-facing domain of the protein, near the hydrophobic stop-transfer membrane-anchor sequence (red), signals cleavage by an endoprotease that simultaneously transfers the carboxyl group of the new C-terminus to the terminal amino group of a preformed GPI anchor. See Figure 3-36a for structure of GPI. [See C. Abeijon and C. B. Hirschberg, 1992, Trends Biochem. Sci. 17:32; I. W. Caras, 1991, J. Cell Biol. 113:77; and K. Kodukula et al., 1992, Proc. Natl. Acad. Sci. USA 89:4982.] * 蛋白质通过不同类型的转运小跑从rER合成部位转运到高尔基体进而分选运至细胞的不同部位，其中涉及各种不同的运输小泡的定向转运，以及膜泡出芽与融合过程。 细胞必须具有有效而精密的机制，确保在rER上合成的各种蛋白，在高尔基体TGN区通过形成不同的转运泡以不同的途径被分选、转运，各就各位，发挥其特殊功能。膜泡运输是蛋白运输的一种特有的方式，普遍存在与真核生物细胞中。在转运过程中涉及蛋白本身的修饰、加工和装配，还涉及到多种不同膜泡定向运输极其复杂的调控过程。 Figure 17-13. The secretory pathway of protein synthesis and sorting. Ribosomes synthesizing proteins bearing an ER signal sequence become bound to the rough ER. As translation is completed on the ER, the polypeptide chains are inserted into the ER membrane or cross it into the lumen. Some proteins (e.g., rough ER enzymes or structural proteins) remain resident in the ER. The remainder move into transport vesicles that fuse together to form new cis-Golgi vesicles. Each cis-Golgi cisterna, with its protein content, physically moves from the cis to the trans face of the Golgi stack (red arrows). As this cisternal progression occurs, many luminal and membrane proteins undergo modifications, primarily to attached oligosaccharide chains. Some proteins remain in the trans-Golgi cisternae, while others move via small vesicles to the cell surface or to lysosomes. In certain cell types (e