ER Membrane Proteins with an N-Terminal Signal Sequence and a Internal Stop-Transfer Sequence (Single Pass Membrane Proteins): Translocation of these proteins proceeds as described above in cotranslational translocation, but midway in the synthesis, a second sequence called a stop-transfer sequence (also an α helix) stops the translocation process. The stop-transfer sequence alters the translocon so that no further translocation occurs. Therefore, the rest of the polypeptide remains on the cytosolic side. The stop transfer α helix passes through the wall of the translocon and into the phospholipid bilayer. When translation is finished, this single pass membrane protein has its N-terminus on the lumen side and its C-terminus on the cytosolic side.