title: Energetics of colicin import revealed by genetic cross-complementation between the Tol and Ton systems.
abstract: Colicins are bacterial toxins that parasitize OM (outer membrane) receptors to bind to the target cells, use an import system to translocate through the cell envelope and then kill sensitive cells. Colicins classified as group A (colicins A, E1-E9, K and N) use the Tol system (TolA, TolB, TolQ and TolR), whereas group B colicins (colicins B, D, Ia, M and 5) use the ExbB-ExbD-TonB system. Genetic evidence has suggested that TolQ and ExbB, as well as TolR and ExbD, are interchangeable, whereas this is not possible with TolA and TonB. Early reports indicated that group B colicin uptake requires energy input, whereas no energy was necessary for the uptake of the pore-forming colicin A. Furthermore, energy is required to dissociate the complex formed with colicin E9 and its cognate immunity protein during the import process. In the present paper, we detail the functional phenotypes and colicin-sensitivity results obtained in tolQ and exbB mutants and cross-complementation data of amino acid substitutions that lie within ExbB or TolQ TMHs (transmembrane helices). We also discuss on a specific phenotype that corresponds to group A colicin-sensitivity associated with a non-functional Tol system.
authors.affiliation: UMR7255 CNRS-Aix-Marseille Université, 31 chemin Aiguier, 13402 Marseille, France. roland.lloubes@imm.cnrs.fr
authors.forename: Roland
authors.initials: R
authors.lastname: Lloubès
authors.forename: Emilie
authors.initials: E
authors.lastname: Goemaere
authors.forename: Xiang
authors.initials: X
authors.lastname: Zhang
authors.forename: Eric
authors.initials: E
authors.lastname: Cascales
authors.forename: Denis
authors.initials: D
authors.lastname: Duché
mesh_terms: D019943:Amino Acid Substitution; D003087:Colicins / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005816:Genetic Complementation Test; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D033903:Periplasmic Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport
chemical_list: D003087:Colicins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D033903:Periplasmic Proteins; D021122:Protein Subunits; C489181:tonB protein, E coli