BIO 320 Lecture Notes - Lecture 4: Atp Hydrolysis, Isopeptide Bond, Endoplasmic-Reticulum-Associated Protein Degradation
Document Summary
Specific combinations of e2s and e3s work on specific substrate proteins. Our genome encodes >600 versions of e3. Degradation signal on target protein allows target protein to bind specific e3. C-terminal glycine of ubiquitin covalently linked to specific lysine side chain of target protein through isopeptide bond. C-terminal glycine of ubiquitin covalently linked to specific lysine side chain of another molecule of ubiquitin through isopeptide bond. For some e3, an extra step is involved. Certain e3s can poly-ubiquitinate specific target proteins, forming ubiquitin chains with specific linkage. Poly-ubiquitination can also involve the other 3 lysines of ubiquitin. Different proteins are modified differently, resulting in different consequences. Specific de-ubiquitinating enzymes can remove ub from specific proteins. K11- and k-48 linked poly-ubiquitinated proteins are degraded in the proteasome, which is made up of many subunits of different types. Core contains protease subunits with active sites facing the cylinder"s inner chamber.
