How the degenerate signal is recognized and delivered in the course of protein translocation across biological membranes.
Protein translocation across a membrane is generally directed by a degenerate signal peptide encoded in the nascent polypeptide chains. Effective signal recognition and the subsequent traversal of the polypeptide chain through the membrane are ensured by the mechanism of cotranslational translocation and/or by chaperone molecules which universally bind to nascent polypeptides and keep them under-structured and translocation-competent. In order to decipher the degenerate signal with a high degree of fidelity, the cells seem to have evolved a multistep signal recognition and relay mechanism, by which a weak, less-specific interaction between individual signal peptides and a defined signal recognition factor can take place, while the highly specific signal delivery can be achieved by only allowing the correct, effective signals to pass through all check-points along the relay cascade. In addition, a "double recognition" and energy-dependent "proof-reading" mechanism may be involved in single steps of such weak-bond interactions.
Yu
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Department of Cell Biology, New York University School of Medicine, New York 10016.
Wang
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D001693:Biological Transport, Active; D004721:Endoplasmic Reticulum / Q000378:metabolism; D017510:Protein Folding; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals; D011506:Proteins / Q000378:metabolism*
D021382:Protein Sorting Signals; D011506:Proteins