Endoplasmic Reticulum

ID #1975

Why is it an incorrect statement when we say that "Signal peptidase cleaves a signal sequence at the amino terminus of the signal peptide". Isn't this statement true? Signal peptidase only cuts the protein at its N-terminus and depending on if a stop transfer sequence is seen later in the amino acid sequence the protein will either become soluble or membrane bound.


If a signal peptidase cut a signal sequence at the amino terminus of the peptide, that would be exactly the same as saying it cut at the N-terminus of the protein. In other words, removing only the amino acid at the very amino terminus of the protein. Signal peptides are much longer than one amino acid, though, and signal peptidase cuts between the amino acid at the carboxy terminus of the signal sequence and the amino terminus of the remainder of the protein.

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