Opening the door to mitochondrial protein import

After reconstitution into liposomes, Tim23p, a mitochondrial inner membrane protein required for protein import, forms an aqueous pore that is activated by a transmembrane potential and mitochondrial targeting peptides. A report in this issue suggests that proteins are translocated into the mitochondrial matrix through a channel formed by Tim23p. These data also suggest a mechanism by which protein import can occur without disrupting the permeablility barrier of the inner membrane.