InterPro domain: IPR023391

The Sec61 complex (eukaryotes) or SecY complex (prokaryotes) forms a conserved heterotrimeric integral membrane protein complex and forms a protein-conducting channel that allows polypeptides to be transferred across (or integrated into) the endoplasmic reticulum (eukaryotes) or across the cytoplasmic membrane (prokaryotes) [ 1 , 2 ]. This complex is composed of alpha, beta and gamma subunits. The alpha-subunits (Sec61-alpha in mammals, Sec61p in Saccharomyces cerevisiae, SecY in bacteria and archaea) and gamma-subunits (Sec61-gamma in mammals, Sss1p in S. cerevisiae, SecE in bacteria and archaea) show significant sequence conservation.

The gamma or SecE subunit consists of two alpha-helices. The N-terminal helix lies on the cytoplasmic surface of the membrane. This helix is amphipathic with the hydrophobic surface pointing towards the membrane, contacting the C-terminal part of the alpha-subunit. This helix is followed by a short beta-strand. The second helix is a long, curved transmembrane helix that crosses the membrane at approximately a 35 degrees angle with respect to the plane of the membrane [ 3 ].

1. X-ray structure of a protein-conducting channel. Nature 427, 36-44
2. The Sec protein-translocation pathway. Trends Microbiol. 9, 494-500