Answer:
The start signal sequence refers to an internal hydrophobic residue that is dissimilar to the signal sequence present at the N-terminal. It associates with the signal receptor particle that combines with the SRP receptor on the membrane. However, unlike the N-terminal signal sequence it is not cleaved.
The stop-transfer signal is also an internal hydrophobic membrane crossing sequence, which follows the start sequence. As soon the translocation machinery comes in contact with the stop-transfer sequence it gets disassembled, the peptide does not get cleaved, however, the translation takes place spontaneously. In this manner, a single start-stop transfer sequence anchors the protein.
