MCD BIO 165A Lecture 14: lecture 14 proteasomes
10 Jan 2019
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Proteasomes: lysosomes destroy aging organelles (autophagy) & material brought into cell from external environment, proteasomes: eliminate abnormal proteins or degradation of individual cellular proteins whose presence is no longer needed. Not an organelle because no membrane; a micromolecular complex. B-subunit has promiscuous proteolytic activity: assume a barrel-shaped form and are present in both the nucleus and cytosol, degradation of protein carried out within hollow cylindrical space. Labeled protein (poly-ubiquitin chain) binds to cap (atpase), force generated by. Enter from cap, denatured -> linear, b-subunit recognizes peptide bond & clips it. Uses atp to drive conformational change in subunits (open/closing gates), Small polypeptides released & recycled recognition of protein into proteasome chamber & protein denaturation, but not needed for protein cleaving. 2 identical rps, one at each end of core particle. Each is made of several different proteins, many of which are atpases. 19s complex: cap = lid + base.
