Notes taken during lecture

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26 Jan 2011
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LECTURE 6
Protein sorting through the secretory pathway
๎€Transfer of proteins into ER lumen
ER โ€“ has translocators embedded in membrane allow for proteins into lumen
From rough ER to Golgi apparatus to other organelles through vesicles
๎€ER first in pathway
Proteins synthesized into lumen of ER become part of inside of lysosome or inside of ER or
secreted outside of cell
Lumenal leaflet is similar to extracellular face of cell
ER is dynamic, a network of tubules that form connections and break old ones
Protein sorting to the ER
๎€In drawining mRNA in blue and green ribosome; nascent polypeptide
synthesizing โ€“ ER signal sequence first translated
๎€Synthesis and modification of proteinsโ€
๎€Synthesis of lipidsโ€ (smooth ER
๎€Have ER signal sequenceโ€
mRNA +ribosomes
๎€Constantly coming to ER membrane and then leaving
๎€Hydrophobic amino acids at N-terminusโ€
Model: Protein sorting
๎€Bind GTPโ€
๎€Low affinityโ€
๎€High affinityโ€
Ribosome
๎€Receptor embedded in the membrane
๎€Translocon in blue
๎€Gated channelโ€
oClosed until ribosome is bound to it, translaiting protein into lumen of ER
๎€Prevent diffusion of ions, small moleculesโ€
๎€GTP hydrolysisโ€
๎€Complex dissociatesโ€
๎€The red signal sequence remains there in the membrane
ER signal sequence
๎€Start-transfer sequenceโ€
๎€Cleaves ER signal sequenceโ€
oEventully degraded
๎€Translocator gated in 2nd direction
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Document Summary

Er has translocators embedded in membrane allow for proteins into lumen. From rough er to golgi apparatus to other organelles through vesicles. Proteins synthesized into lumen of er become part of inside of lysosome or inside of er or secreted outside of cell. Lumenal leaflet is similar to extracellular face of cell. Er is dynamic, a network of tubules that form connections and break old ones. In drawining mrna in blue and green ribosome; nascent polypeptide synthesizing er signal sequence first translated. constantly coming to er membrane and then leaving. Translocon in blue: closed until ribosome is bound to it, translaiting protein into lumen of er. The red signal sequence remains there in the membrane. cleaves er signal sequence : eventully degraded. D signal recognition particle first binds, then translocator channel holds onto it. pluses always on cytosol help predict whether n or c-terminus.

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