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Regulated protein degradation

Regulated protein degradation - Regulated protein...

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Regulated protein degradation (Lodish page 86-88, 600-602, 612-617; Alberts Page 391-397) I. Two pathways in regulated protein degradation A. Ubiquitin mediated protein degradation, mostly for soluable proteins B. Protein degradation in the lysosomes, for membrane protein, cytosolic proteins and endocytosed proteins. II. Ubiquitination A. Discovery of ubiquitin B. Ubiquitin is a 76 aa peptide that can be covalently attached to substrate proteins, a post- translational protein modification similar to phosphorylation, it can be added and removed (Alberts Fig. 6-92a). C. Ubiquitin functions in regulated protein degradation and proteasome independent functions of ubiquitin in the secretory/endocytic pathways. D. Mono- and poly-ubiquitination (Alberts Fig. 6-93) a. Polyubiquitin chains of at least 4 Lys48-linked ubiquitins targets substrate for proteasome degradation. Protein turnover in the cytoplasm is mediated by ubiqutination and proteasome degradation. Abnormal or misfolded proteins are destroyed; some normal proteins are naturally short-lived or conditionally short lived in a regulated manner. Many misfolded newly synthesized proteins in the secretory pathway are retro-translocated from the ER, tagged with ubiquitin, and degraded in the cytoplasm by the proteasome; this pathway is called ER-associated degradation (Alberts Fig. 12-54).
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