Barreling through the outer membrane

The protein translocation channel of the outer mitochondrial membrane is thought to be a rigid P-barrel, Newly synthesized membrane proteins apparently do not escape laterally from this channel into the lipid bilayer, but must insert into the outer membrane from the aqueous phase. A study on the biogenesis of the mitochondrial outer membrane translocation machinery now shows that the subunit forming the protein import channel is first translocated across the outer membrane and then reinserted.