Sec61

Sec61, termed SecYEG in prokaryotes, is a membrane protein complex found in all domains of life. 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). It has a region called the plug that blocks transport into or out of the ER. This plug is displaced when the hydrophobic region of a nascent polypeptide interacts with another region of Sec61 called the seam, allowing translocation of the polypeptide into the ER lumen. Although SecY and SecE are conserved in all three domains of life, bacterial SecG is only weakly homologous with eukaryotic Sec61β. The eukaryotic Sec61β is however homologous to the archaeal "SecG", leading some authors to refer to the archaeal complex as SecYEβ instead of SecYEG. (All three components of the archaeal complex are closer to their eukaryotic homologues than to their bacterial ones, but the old two-empire names have become convention.)

Sec61, termed SecYEG in prokaryotes, is a membrane protein complex found in all domains of life. 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). It has a region called the plug that blocks transport into or out of the ER. This plug is displaced when the hydrophobic region of a nascent polypeptide interacts with another region of Sec61 called the seam, allowing translocation of the polypeptide into the ER lumen. Although SecY and SecE are conserved in all three domains of life, bacterial SecG is only weakly homologous with eukaryotic Sec61β. The eukaryotic Sec61β is however homologous to the archaeal "SecG", leading some authors to refer to the archaeal complex as SecYEβ instead of SecYEG. (All three components of the archaeal complex are closer to their eukaryotic homologues than to their bacterial ones, but the old two-empire names have become convention.) ==Species-specifics== Human proteins: SecY: SEC61A1, SEC61A2 SecG: SEC61B SecE: SEC61G Budding yeast have two such homologous complexes; the essential one is named Sec61, and the non-essential one is called Ssh1. Like Sec61, Ssh1 does dock to the ribosome.

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