Measuring Endoplasmic Reticulum Signal Sequences Translocation Efficiency Using the Xbp1 Arrest Peptide.

Secretory proteins translocate across the mammalian ER membrane co-translationally via the ribosome-sec61 translocation machinery. Signal sequences within the polypeptide, which guide this event, are diverse in their hydrophobicity, charge, length, and amino acid composition. Despite the known sequence diversity in the ER signals, it is generally assumed that they have a dominant role in determining co-translational targeting and translocation process.