title: Border crossings: colicins and transporters.
abstract: Colicins are protein toxins produced by Escherichia coli to kill related bacteria. They must cross the target cell outer membrane (OM), and some must also cross the inner membrane (IM). To accomplish cellular import, colicins have parasitized E. coli nutrient transporters as well as IM and periplasmic proteins normally used to maintain cell wall integrity or provide energy for nutrient uptake through transporters. Colicins have evolved to use both transporters and other membrane proteins through mechanisms different from those employed in physiological substrate uptake. Extended receptor-binding domains allow some colicins to search by lateral diffusion for binding sites on their OM translocators while bound to their primary OM receptor. Transport across the OM is initiated by entry of the unstructured N-terminal translocation domain into the translocator. Periplasmic and IM networks subsequently accomplish insertion of the colicin cytotoxic domain into or across the IM.
authors.affiliation: Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, New York 10461, USA. karen.jakes@einstein.yu.edu
authors.forename: Karen S
authors.initials: KS
authors.lastname: Jakes
authors.forename: William A
authors.initials: WA
authors.lastname: Cramer
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism*; D003087:Colicins / Q000378:metabolism*; D004734:Energy Metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D019897:Periplasm / Q000235:genetics / Q000378:metabolism; D018272:Porins / Q000378:metabolism; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D021381:Protein Transport
chemical_list: D001425:Bacterial Outer Membrane Proteins; D003087:Colicins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C109237:OmpF protein; D018272:Porins; C062093:tolA protein, E coli; C073126:tolC protein, E coli; C489181:tonB protein, E coli