细胞生物学 教学课件 ppt 作者 李瑶 主编第5章 细胞内膜系统 上课件.ppt

* * O-linked oligosaccharides: Formed by the sequential transfer of sugars from nucleotide precursors Amino acids: -OH of Ser、Thr、Hyp Sugars: galactose or N-acetylglucosamine Short, 1-4 sugars residues Golgi apparatus N-linked oligosaccharides: Begin with addition of an oligosaccharide with 14 sugars (dilichol) in the ER Subsequently certain sugar residdues are removed and others are added Only Asn in Asn-x-Thr or Asn-x-Ser was modified Modifications to N-linked oligosaccharides are completed in the Golgi apparatus * * The functions of glycosylation Protect proteins from enzyme digestion Proper folding Play a role in cell-cell adhesion * * Processing of N-linked oligosaccharides in the Golgi * * 高尔基体膜囊中进行的蛋白质糖基化和转运 * * Protein Sorting * * Protein quality control Several strategies are used to ensure that only proteins properly folded or targeted to other organelles are transported ERAD: ER-associated protein degradation UPR: unfolded protein response Many ER-resident proteins contain a Lys-Asp-Glu-Leu (KDEL) sequence. The KDEL receptor retrieve proteins with the KDEL recognition sequence through COPI vesicle transportation * * 胰岛素原的加工 Figure 13-35 Molecular Biology of the Cell (? Garland Science 2008) 高尔基体的发生 * * * * * * * * * * * * * * * * * * * * * * Figure 12-45 Molecular Biology of the Cell (? Garland Science 2008) * * ?跨膜信号与膜蛋白的定向 ◆单次跨膜蛋白 ●起始转移信号(start transfer signal) ●终止转移序列(stop transfer sequence) ●可切割的信号序列(Cleavable signal sequence) (N-端) ●内部信号序列(internal signal sequence) (internal noncleavable signal sequences ) Figure 12-46 Molecular Biology of the Cell (? Garland Science 2008) Figure 12-47 Molecular Biology of the Cell (? Garland Science 2008) Figure 12-48 Molecular Biology of the Cell (? Garland Science 2008) Figure 12-49 Molecular Biology of the Cell (? Garland Science 2008) Figure 12-58 Molecular Biology of the Cell (? Garland Science 2008) * * ◆蛋白质在内质网中的加工与修饰 ●The formation of disulfide bonds between the side