生物化学课件§3 3D Structure of Proteins.pptVIP

liguofu liguofu Five constraints affecting the stability of a-helix Quaternary structures symmetry Capsid of tobacco mosaic virus: the virus-encapsulating cylindrical structure is a right-handed helical filament made up of 2,130 identical subunits. Size limit: ? the genetic coding capacity; ? the error frequency during protein biosynthesis Human poliovirus (脊髓灰质炎病毒) §3 3D Structure of Proteins §3.1 Overview of Protein Structure §3.2 Protein Secondary Structure §3.3 Tertiary Quaternary Structure §3.4 Protein Denaturation Folding §3.4 Protein Denaturation Folding Loss of structure results in loss of function Denaturation of some proteins is reversible Polypeptides fold rapidly by stepwise process Death by misfolding: the prion Protein folding in vivo 在活的有机体内 Loss of structure results in loss of function Denaturant变性剂: Destroy hydrophobic interaction: 去垢剂，有机溶剂等 Destroy H bonds Destroy static electrical force Temperature 尿素、胍盐、酸、碱 Denaturation of some proteins is reversible Polypeptides fold rapidly by stepwise process Death by misfolding: the prion diseases (1) Normal brain tissue Spongy brain tissue Transmissible Spongiform Encephalopathies Animal Scrapie:羊搔痒病 BSE (bovine spongiform encephalopathy) (Mad cow disease ) Human CJD: Creutzfeld-Jacob Disease，克雅氏病 GSS: Gerstmann-Straussler-Scheinker syndrome， GSS综合症 FFI: Fatal familial Insomnia，致死性家庭失眠症 Kuru：库鲁病 Alpers Syndrome Death by misfolding: the prion diseases (3) 1982，Stanley B. Prusiner coined the word “prion” refer to “protein infectious particle” 1997， Stanley B. Prusiner won the Nobel Prize in Physiology or Medicine Death by misfolding: the prion diseases (4) PrPC PrPSC PrP ＝ Prion Protein C ＝ Cellular Sc ＝ Scrapie PrPSC further induces PrPC into PrPSC Need： Protein disulfide isomerase (PDI） Peptidyl prolyl isomerases (PPIases) Molecular chaperones are proteins that interact with partially folded or improperly folded polypeptides, facilitating correct folding pathways or providing mic