Endoplasmic Reticulum

ID #1280

What causes the protein to be cleaved off into the lumen? In other words, what signal determines whether the protein will stay within the lumen or become a transmembrane protein?

By this point in the semester, it shouldn't come as a surprise that it comes down to a specific signal. Signal peptidase is looking for a particular strech of amino acids, and it's going to find it in an amino terminal signal peptide. Not the whole peptide itself, but some of the amino acids that are part of the signal sequence and some amino acids that are part of the "rest" of the protein. It knows what amino acids to cut between, and does so very efficiently.

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