As the core component of the translocon, it transports proteins to the endoplasmic reticulum in eukaryotes and out of the cell in prokaryotes.
It is a doughnut-shaped pore through the membrane with 3 different subunits (heterotrimeric), SecY (α), SecE (γ), and SecG (β).
[1] Although SecY and SecE are conserved in all three domains of life, bacterial SecG is only weakly[citation needed] homologous with eukaryotic Sec61β.
In the middle of the membrane is a construction, formed from a pore ring of four[citation needed] hydrophobic amino acids that project their side chains inwards.
[2] The bacterial SecYEG channel interacts with the signal sequences of secretory proteins as well as SecA, an ATPase which drives translocation.
[6] Human proteins: Budding yeast have two such homologous complexes; the essential one is named Sec61, and the non-essential one is called Ssh1.