Multiple protein transporters 14 13 mitochondrial

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Unformatted text preview: ial protein targeting: multiple protein transporters Mitochondrial protein targeting: multiple protein transporters 14 13 Mitochondrial protein targeting: chaperones and H+ gradient Two routes to the mitochondrial inner membrane 15 16 Nuclear localization signals (NLSs) direct proteins to the nucleus Proteins enter the nucleus through the nuclear pore complex (NPC) The NLS is located internally and is not cleaved o (why?) The NPC is perhaps the largest protein complex in the cell. It consists of multiple copies of >30 di erent proteins arranged in 8-fold symmetry. It’s mass is ~50X the mass of the ribosome! 17 18 The mechanism of nuclear transport NPC fun facts and gures Mass: ~125 MDa Typical mammalian cell: ~3000 NPCs During DNA synthesis: one NPC imports 106 histones/min During rapid cell growth: one NPC exports 6 ribosomes/min This slide is just to help you succeed at the next trivia night at a local pub. You will not be tested on this information. 19 20 The secretory pathway The secretory pathway prepares and packages proteins for secretion cytoplasm Examples: Many, many proteins are secreted from cells hormones, e.g., insulin, EPO low density lipoprotein (LDL) blood albumin 30% of the genes in your genome encode membrane proteins blood clo ing proteins antibodies cytoplasm snot (mucus) How are proteins embedded into membranes? connective tissue proteins digestive enzymes How are others secreted across membranes? spider silk extracellular space David Goodsell exocytosis 22 21 The secretory pathway also inserts and folds integral membrane proteins Secreted and integral membrane proteins are sequentially transported into and through ER and Golgi compartments, then transported to nal destinations cytoplasm • ion channels • nutrient transporters • hormone receptors • neurotransmi er receptors • cell adhesion molecules protein folding endoplasmic reticulum (ER) glycosylation (addition of carbohydrates to proteins) formation of disul de (—S-S—) bonds between pairs of cysteine residues quality control (veri cation of folding) cytoplasm Review: Prof. Brzovic, Lecture 2 Golgi complex oily (hydrophobic)core of lipid bilayer cis medial trans remodeling of glycosyl modi cations packaging into vesicles for routing of di erent proteins to speci c nal destinations extracellular space 23 packaging into vesicles for transport to Golgi exocytosis 24 0.1164; IRMOF-16, cubic, Pm-3m, a 3 Sciences Engineering) for supplying a sample of the 2 Downloaded from www.sciencemag.org on March 2, 2008 4 Regular light 6. Light microsco- E f ADF-3 His and -3 fibers spun 12% and 22% ) rc– spider silk ein solutions, retively. Fibers exed birefringence had an average fiPolarizing light diameter of 20 (A and C) Regular light microscopy for -3 His and ADF-3 fibers, respectively. (B D) Polarizing light microscopy with a 530first-order red plate for ADF-3 His and -3, respectively. (E) ADF-3 fiber spun from % (w/v) rc– spider silk protein solution in anol, then drawn fourfold in methanol...
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