分子生物学英文课件：chapter17-Biosynthesis of Proteins.ppt

Features of signal peptide: (1) positively charged amino acid residues, usually near the amino terminus; (2) a sequence of hydrophobic amino acids, typically 10 to 15 residues long; (3) a short sequence at the C terminus, which are polar AA with short side chain (especially Ala), close to the cleavage site (recognized by signal peptidase). 3. Mitochondria proteins proteins destined to the mitochondria have signal sequences, at the N terminus of the proteins and are cleaved once the proteins arrive at their final destinations. 2. Endoplasmic reticulum proteins proteins destined to the ER have signal sequences, at the C terminus of the proteins. 4. Membrane proteins 囊泡形成和转运 5. transport pathway for nucleus proteins The signal sequence that destined to the nucleus are located internally and are not cleaved. These signals permit proteins to enter the nucleus rapidly through nuclear pores. The nuclear importin αandβfunction as the nucleus proteins receptor, a small GTPase Ran is required. Section Ⅴ. Interference and Inhibition of Protein Biosynthesis I. Antibiotics inhibit protein synthesis Many effective antibiotics interact specifically with the proteins of prokaryotic ribosomes and can be exploited for clinical purpose. eg. tetracyclines, chloramphenicol, streptomycin, lincocin Some antibiotics inhibit protein synthesis on all ribosomes or only on those of eukaryotes and are used for research purpose. 抗生素 作用位点 作用原理 应用 伊短菌素 原核、真核核蛋白体小亚基 阻碍翻译起始复合物的形成 抗病毒药 四环素、土霉素 原核核蛋白体小亚基 抑制氨基酰-tRNA与小亚基结合 抗菌药 链霉素、新霉素、巴龙霉素 原核核蛋白体小亚基 改变构象引起读码错误、抑制起始 抗菌药 氯霉素、林可霉素、红霉素 原核核蛋白体大亚基 抑制转肽酶、阻断肽链延长 抗菌药 嘌呤霉素 原核、真核核蛋白体 使肽酰基转移到它的氨基上后脱落 抗肿瘤药 放线菌酮 真核核蛋白体大亚基 抑制转肽酶、阻断肽链延长 医学研究 夫西地酸、细球菌素 EF-G 抑制EF-G、阻止转位 抗菌药 壮观霉素 原核核蛋白体小亚基 阻止转位 抗菌药 常用抗生素抑制肽链生物合成的原理与应用 四环素族 氯霉素 链霉素和卡那霉素 嘌呤霉素 放线菌酮 Large subunit Small subunit 红霉素 嘌呤霉素作用示意图 Ⅱ. Some toxin can inhibit biosynthesis of eukaryote Diphtheria toxin : NAD＋ Pr. Kinase induced by interferon dsRNA (1). Ind