Elongation factor Tu and DnaK are transferred from the cytoplasm to the periplasm of Escherichia coli during osmotic downshock presumably via the mechanosensitive channel MscL

Upon osmotic downshock, a few cytoplasmic proteins, including thioredoxin, elongation factor Tu (EF-Tu), and DnaK, are released from Tris-EDTA-treated Escherichia coli cells by an unknown mechanism. We have shown previously t hat deletion of mscL, the gene coding for the mechanosensitive channel of t he plasma membrane,vith the highest conductance, prevents the release of th ioredoxin. We confirm and extend the implication of MscL in this process by showing that the release of EF-Tu and DnaK is severely impaired in MscL-de ficient strains. Release of these proteins is not observed in the absence o f a Tris-EDTA treatment which disrupts the outer membrane, indicating that, in intact cells, they are transferred to the periplasm upon shock, presuma bly through the MscL channel.