MICR 3230 Chapter Notes - Chapter 8: Chromosome, Endosome, Tapasin
9 Nov 2016
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Chapter 8: the major histo(cid:272)o(cid:373)pati(cid:271)ilit(cid:455) co(cid:373)ple(cid:454) a(cid:374)d a(cid:374)tige(cid:374) prese(cid:374)tatio(cid:374) The endogenous pathway of antigen processing and presentation. Constant turnover of proteins in eukaryotic cells due to half-lives and denatured, misfolded and abnormal proteins. Consequence is that there are constantly degradation products within a cell; some degraded to aa"s and reused, whole others remain in cytosol as peptides. Cell samples the peptides and present some on the plasma membrane with class i mhc, where immune cells can survey for foreign proteins. Peptides are generated by protease complexes called proteasomes. Intracellular proteins are degraded into short peptides by cytosolic proteolytic system present in all cells, called the proteasome. Large 20s proteasome: 14 subunits arrayed in a barrel-like structure of symmetrical rings. Proteins are targeted for proteolysis when a small protein, ubiquitin is attached to them. Ubiquitin-protein conjugates enter proteasome complex, consisting of 20s base and attached 19s regulatory component, through a narrow channel at the 19s end.
