蛋白质的转译後修饰作用.PDF

蛋白質的轉譯後修飾作用 國立臺灣大學生化科技學系張世宗 shihchung@ntu.edu.tw The Extra Eppisode of Central DogmaCentral Dogma: Post-translational MModifidificatition Coupling of transcription and translation in bacteria Lehninger Principles of Biochemistry 5th edition Directing eukaryotic proteins with the appropriate signals to the ER Lehninger Principles of Biochemistry 5th edition Some proteins undergo assisted folding Molecular chaperone 分子伴護蛋白，如Hsp70, Hsp40 ■結合疏水性及unfolded區域，或newly synthesized but not yet folded peptide chains ， 以保護其不被降解或防止不當的聚集與沈澱以保護其不被降解或防止不當的聚集與沈澱。 ■維持某些蛋白質於unfolded型態，以利於穿膜運輸 ■■加速蛋白質四級結構的形成加速蛋白質四級結構的形成 Chaperonin (Cpn) 伴護蛋白，如Hsp60, Hsp10, Cpn60, Cpn10 ■■ 直接促進蛋白質的摺疊直接促進蛋白質的摺疊 Protein disulfide isomerase (PDI) ■■ CatalyzesCatalyzes thethe interchangeinterchange, oror shufflingshuffling, ofof disulfidedisulfide bondsbonds untiluntil thethe bondsbonds ofof nativenative conformation are formed. ■ Catalyzes the elimination of folding intermediates with inappropriate disulfide crosslinks. Peptide prolyl cis-trans isomerase (PPI) ■■ IIntterconversiion off ciis andd ttrans iisomers off PPro resididue peptidtide bbondds can bbe a sllow step in the folding of proteins that contain some Pro peptide bonds in the cis conformation. 蛋白質轉譯出來之後要靠 chaperone 幫助正確摺疊 Alberts et al (2002) Molecular Biology of the Cell (4e) p.357 摺疊不良的蛋白質會被送到蛋白體降解系統 Probing the proteasome pathway (2000) Alfred L. Goldberg, Nature Biotechnology 18, 494-496 相似的桶狀巨分子卻有相反的功能 內部折疊區 內部內部水解水解區區 Proteasome (20S)Proteasome (20S) ChChaperoniin ((GGroELEL))