title: Colicin A and the Tol proteins involved in its translocation are preferentially located in the contact sites between the inner and outer membranes of Escherichia coli cells.
abstract: Colicin A is a bacterial toxin which forms channels in the cytoplasmic membrane of Escherichia coli. Its translocation through the envelope requires the participation of bacterial proteins encoded by the tolQ, -R, -A, and -B genes. Overproduction of the Tol proteins decreased the time needed for colicin A translocation and increased the number of channels formed in vivo. Cells overproducing radioactively labeled Tol proteins and containing or not colicin A were fractionated. The Tol proteins were mainly recovered in the inner membrane and in the contact sites between the two membranes. The presence of colicin A increased the specific radioactivity of the Tol proteins in the contact sites. Our data suggest that the Tol proteins form a complex of definite stoichiometry in the membranes and that colicin A is associated to this complex upon channel formation. We discuss the possibility that the channel activity determined in vivo is due to the colicin A-Tol proteins complex.
authors.affiliation: Laboratoire des Biomembranes, URA 1116 Centre National de la Recherche Scientifique, Université Paris Sud, Orsay, France.
authors.forename: G
authors.initials: G
authors.lastname: Guihard
authors.forename: P
authors.initials: P
authors.lastname: Boulanger
authors.forename: H
authors.initials: H
authors.lastname: Bénédetti
authors.forename: R
authors.initials: R
authors.lastname: Lloubés
authors.forename: M
authors.initials: M
authors.lastname: Besnard
authors.forename: L
authors.initials: L
authors.lastname: Letellier
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D003087:Colicins / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D003087:Colicins