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Figure 9.11. Insertion of a membrane protein with a cleavable signal sequence and a single stop-transfer sequence.

Figure 9.11Insertion of a membrane protein with a cleavable signal sequence and a single stop-transfer sequence

The signal sequence is cleaved as the polypeptide chain crosses the membrane, so the amino terminus of the polypeptide chain is exposed in the ER lumen. However, translocation of the polypeptide chain across the membrane is halted by a transmembrane stop-transfer sequence that closes the Sec61 translocation channel and exits the channel laterally to anchor the protein in the ER membrane. Continued translation results in a membrane-spanning protein with its carboxy terminus on the cytosolic side.

From: The Endoplasmic Reticulum

Cover of The Cell
The Cell: A Molecular Approach. 2nd edition.
Cooper GM.
Sunderland (MA): Sinauer Associates; 2000.
Copyright © 2000, Geoffrey M Cooper.

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