The Role of EMC during Membrane Protein Biogenesis

Membrane proteins are topologically, structurally, and biophysically diverse and constitute ~20% of protein coding genes in all organisms. Their membrane insertion, folding, and assembly with other proteins are processes essential for all organisms. The EMC is an abundant protein complex in the ER of eukaryotes. Its disruption has pleiotropic phenotypes in all organisms examined. The phenotypes often impact the abundance or localization of membrane proteins. Among the proteins impacted by EMC loss are tail-anchored proteins and GPCRs. In both cases, EMC mediates the insertion of a transmembrane domain near the N terminus (for GPCRs) or C terminus (for tail-anchored proteins). EMC also interacts with other types of membrane proteins transiting through the ER and might participate in either their folding or assembly by serving as a chaperone