N-terminus and C-terminus signal sequence

A Double Pass transmembrane protein has an Internal ER signal sequence

Internal Sequence acts as a hydrophobic Start-Transfer Signal and helps anchor final protein, and is recognized by an SRP which bings ribosome to ER membrane

When a hydrophobic Stop-Transfer Sequence enters the translocation channel, the channel discharges both sequences into the lipid bilayer.

Neither the stop or start transferis cleaved off and the entire peptide chain remains anchored int eh membrane as a double pass transmembrane protein

Single-Pass transmembrane protein is retained in the Lipid Bilayer

N-terminal ER Signal sequence initiates transfer. Th eproteins also contains second hydrophobic sequence, which acts as a stop-transfer sequence, this sequence enters teh translocation Channel and discharges growoing polpeptide chain sideways into the lipid bilayer.

The N-terminal signal sequence is cleabed off leaving the transmembrane protein anchored in the membrane. Protein synthesis onteh cytosolic side then continues to completion