Structural basis for membrane insertion by the human ER membrane protein complex

A defining step in the biogenesis of a membrane protein is the insertion of its hydrophobic transmembrane helices into the lipid bilayer. The nine-subunit endoplasmic reticulum (ER) membrane protein complex (EMC) is a conserved co- and posttranslational insertase at the ER. We determined the structure of the human EMC in a lipid nanodisc to an overall resolution of 3.4 angstroms by cryo–electron microscopy, permitting building of a nearly...