11 The Endoplasmic Reticulum

11 The Endoplasmic Reticulum - BME 418, Quantitative Cell...

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BME 418, Quantitative Cell Biology Alan J. Hunt General problem: how do we get proteins to appropriate targets? Specific issues: - Membrane proteins denature if not immediately inserted in membrane. - Enzymes could damage cells if expressed in inappropriate locations. - Proteins that belong in intracellular compartments (lysosomes, mitochondria, etc.) cannot gain access by diffusion. General Solution: Signal Sequences. - short, typically less than 10 aa's - ribosomes same on ER or in solution, targeting after sequence is translated R.E.R. - rough appearance due to ribosomes - if a ribosome begins synthesis of a protein expressing an ER signal peptide it becomes associated with the ER - protein is passed through membrane during synthesis i) stays embedded in membrane (membrane proteins) ii) released into ER lumen.
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BME 418, Quantitative Cell Biology Alan J. Hunt Whether the protein is released or remains in membrane again depends on the signal sequence. How does this work? Depends on signal-recognition particle (SRP) and SRP receptor: - SRP binds signal peptide - SRP receptor and ribosome receptor bind ribosome-mRNA-peptide complex
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This note was uploaded on 09/06/2008 for the course BIOMEDE 418 taught by Professor Hunt during the Winter '08 term at University of Michigan.

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11 The Endoplasmic Reticulum - BME 418, Quantitative Cell...

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