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Joined 2026-09-21 Message
Incoming links: Tail-anchored protein
Cotranslational protein translocation 2026-10-18
Cotranslational protein translocation is passage of a growing polypeptide chain across a membrane during biological translation. SRP recognizes an exposed hydrophobic ER signal sequence. The SRP receptor enables handoff to the Sec61 complex. Biological translation can slow during delivery; the ribosome remains on the cytosol side.[ref]
Membrane Protein Insertion at the Endoplasmic Reticulum by Sichen Shao and Ramanujan S. Hegde. Shao and Hegde, Membrane Protein Insertion at the Endoplasmic Reticulum, 2011; “Cotranslational Targeting”, Figure 3
The useful engineering feature is coordination: a targeting instruction can become accessible while the rest of its cargo is still being made. Recognition, docking and crossing remain distinct operations. A defect in any one can prevent successful import even when the protein primary structure contains an appropriate signal.
This route is not universal. Many tail-anchored proteins use delivery after biological translation, and their membrane-spanning segment lies near the C-terminus. Thus protein targeting signals need not be at the N-terminus.[ref]
Membrane Protein Insertion at the Endoplasmic Reticulum by Sichen Shao and Ramanujan S. Hegde. Shao and Hegde, 2011; “Posttranslational Membrane Protein Topogenesis”, Figure 6
Tail-anchored protein 2026-10-18
A tail-anchored protein has a membrane-spanning segment near its C-terminus; many reach the endoplasmic reticulum after biological translation.