Membrane protein insertase YidC in bacteria and archaea

Summary The insertion of proteins into the prokaryotic plasma membrane is catalyzed by translocases and insertases. On one hand, the Sec translocase operates as a transmembrane channel that can open laterally to first bind and then release the hydrophobic segments of a substrate protein into the lipid bilayer. On the other hand, YidC insertases interact with their substrates in a groove‐like structure at an amphiphilic protein–lipid interface thus allowing the transmembrane segments of the substrate to slide into the lipid bilayer. The recently published high‐resolution structures of YidC provide new mechanistic insights of how transmembrane proteins achieve the transition from an aqueous environment in the cytoplasm to the hydrophobic lipid bilayer environment of the membrane. The insertion of proteins into the prokaryotic plasma membrane is catalyzed by translocases and insertases. On one hand, the Sec translocase operates as a transmembrane channel that can open laterally to first bind and then release the hydrophobic segments of a protein into the lipid bilayer. On the other hand, YidC insertases interact with their substrates in a groove‐like structure at an amphiphilic protein‐lipid interface thus allowing the transmembrane segments of the substrate to slide into the lipid bilayer. We review here the recently published high‐resolution structures of archaeal and bacterial YidC homologues that provide new mechanistic insights of how transmembrane proteins achieve the transition from an aqueous environment in the cytoplasm to the hydrophobic lipid bilayer environment of the membrane.