Periplasmic accumulation of truncated forms of outer-membrane PhoE protein of Escherichia coli K-12.

In order to localize the information within PhoE protein of Escherichia coli K-12 required for export of the protein to the outer membrane, we have generated deletions throughout the phoE gene. Immunocytochemical labelling on ultrathin cryosections revealed that the polypeptides encoded by the mutant alleles are transported to, and accumulate in, the periplasm. These results show that, except for the signal sequence, there is no specific sequence within the PhoE protein that is essential for transport through the cytoplasmic membrane. The overall structure of the protein, rather than a particular sequence of amino acids, seems to be important for assembly into the outer membrane.