Protein import into Escherichia coli: colicins A and E1 interact with a component of their translocation system.
Colicins are antibiotic proteins that kill sensitive Escherichia coli cells. Their mode of action involves three steps: binding to specific receptors located in the outer membrane, translocation across this membrane, and action on their targets. A specific colicin domain can be assigned to each of these steps. Colicins have been subdivided into two groups (A and B) depending on the proteins required for them to cross the external membrane. Plasmids were constructed which led to an overproduction of the Tol proteins involved in the import of group A colicins. In vitro binding of overexpressed Tol proteins to either Tol-dependent (group A) or TonB-dependent (group B) colicins was analyzed. The Tol dependent colicins A and E1 were able to interact with TolA but the TonB dependent colicin B was not. The C-terminal region of TolA, which is necessary for colicin uptake, was also found to be necessary for colicin A and E1 binding to occur. Furthermore, only the isolated N-terminal domain of colicin A, which is involved in the translocation step, was found to bind to TolA. These results demonstrate the existence of a correlation between the ability of group A colicins to translocate and their in vitro binding to TolA protein, suggesting that these interactions might be part of the colicin import process.
Benedetti
H
H
Centre de Biochimie et de Biologie Moléculaire du CNRS, Marseille, France.
Lazdunski
C
C
Lloubès
R
R
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001692:Biological Transport; D015153:Blotting, Western; D003087:Colicins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family; D010641:Phenotype; D010957:Plasmids
D001426:Bacterial Proteins; D003087:Colicins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C062093:tolA protein, E coli; C057616:tonB protein, Bacteria; C489181:tonB protein, E coli