考研资料：北京大学细胞生物学第六章节基质与内膜下课件幻灯片.pptVIP

作 业 膜泡表面标志与膜泡运输 过氧化物酶体中蛋白质的来源及输入机制 尚辅网 / B. Signal Hypothesis --G.Blobel D.Sabatini,1971. A model for the Signal Mechanism of Cotranslational Import Evidence That Protein Synthesized on Ribosomes Attached to ER Membranes Pass Directly into the ER Lumen (D.Sabatini) Milstein : IgG Milstein et al: Studying the synthesis of light chain of IgG (in cell-free systems, 20 Aa longer at N-terminal end than the authentic light chain ) Adding ER membranes to this system leads to the production of an IgG light chain of the correct size. A Schematic model for the synthesis of a secretory protein on a membrane-bound ribosome of the rough ER Signal-recognition particle, SRP: Six different polypeptides complexed with a 300-nucleotide (7S)molecule of RNA. ER signal sequence: Typically 15-30 amino acids: Consist of three domains: a positively charged N-terminal region, a central hydrophobic region, and a polar region adjoining the site where cleavage from the mature protein will take place. A signal sequence on nascent seretory proteins targets them to the ER and is then cleaved off SRP receptor (GTP binding protein) SRP have three main active sites: One that recognizes and binds to ER signal sequence; One that interacts with the ribosome to block further translation; One that binds to the ER membrane (docking protein)) The sorting signal of VSV glycoproteins : Asp-X-Gln或DXE Figure 6-43. The sorting of proteins destined for the apical and basolateral plasma membranes of epithelial cells. When cultured MDCK cells are infected simultaneously with VSV and influenza virus, the VSV glycoprotein is found only on the basolateral membrane, whereas the HA glycoprotein of the influenza virus is found only on the apical membrane. Like these viral proteins, some cellular proteins are sorted directly to the apical membrane and others to the basolateral membrane via specific transport vesicles that bud from the trans-Golgi network. In c