MCDB428lect07 - MCDB 428 Lecture 6: Wednesday January 16,...

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Lecture 6: Wednesday January 16, 2008 Today’s Outline Membrane Potential revisited Protein Targeting Cytosolic ribosomes ER-associated ribosomes Signal-hypothesis ER signal peptide Presequence, transit peptide Nuclear Localization sequence ER targeting and protein translocation Elements of the translocon Co-translational translocation Post-translational translocation Type I-III proteins GPI-anchored proteins MCDB 428
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Membrane Potential: An Introduction Membrane is now permeable to Na + Cytosol Na + = 15 mM Extracellular Na + = 150 mM << Electric potential is positive because more Na+ outside than in log10(extracell/cytosol) extracell/cytosol = >1, log10(>1) = positive In vivo, ~90% of membrane potential is generated by the K+ ion gradient. K+ in cytosol is ~140 mM, in extracellular space its ~4 mM. As a result, log10(extracell/cytosol) extracell/cytosol = <1, log10(<1) = negative
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ER-destined proteins are translated by ribosomes attached to cytosolic face of ER membrane
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This note was uploaded on 09/03/2009 for the course MCDB 428 taught by Professor Wang during the Winter '08 term at University of Michigan.

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MCDB428lect07 - MCDB 428 Lecture 6: Wednesday January 16,...

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