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Short Video: Cotranslational Transport

by Pearson
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Proteins that are targeted for translocation across the ER during cotranslational import have an amino-terminal signal sequence (yellow), which is recognized by the signal recognition particle (SRP). The ribosome is targeted to the ER membrane starting with the binding of the SRP by the SRP receptor. The signal sequence of the nascent peptide chain is then transferred to a protein channel as the SRP dissociates from the ribosome and the SRP receptor, which requires GTP hydrolysis. The signal sequence of the nascent peptide intercalates into the walls of the translocation channel, through a side opening. During translocation, the signal sequence is cleaved by a signal peptide peptidase, freeing the amino terminus of the growing peptide. Credit: Janet Iwasa, Harvard Medical School
Proteins that are targeted for translocation across the ER during cotranslational import have an amino-terminal signal sequence (yellow), which is recognized by the signal recognition particle (SRP). The ribosome is targeted to the ER membrane starting with the binding of the SRP by the SRP receptor. The signal sequence of the nascent peptide chain is then transferred to a protein channel as the SRP dissociates from the ribosome and the SRP receptor, which requires GTP hydrolysis. The signal sequence of the nascent peptide intercalates into the walls of the translocation channel, through a side opening. During translocation, the signal sequence is cleaved by a signal peptide peptidase, freeing the amino terminus of the growing peptide. Credit: Janet Iwasa, Harvard Medical School