title: Colicin biology.
abstract: Colicins are proteins produced by and toxic for some strains of Escherichia coli. They are produced by strains of E. coli carrying a colicinogenic plasmid that bears the genetic determinants for colicin synthesis, immunity, and release. Insights gained into each fundamental aspect of their biology are presented: their synthesis, which is under SOS regulation; their release into the extracellular medium, which involves the colicin lysis protein; and their uptake mechanisms and modes of action. Colicins are organized into three domains, each one involved in a different step of the process of killing sensitive bacteria. The structures of some colicins are known at the atomic level and are discussed. Colicins exert their lethal action by first binding to specific receptors, which are outer membrane proteins used for the entry of specific nutrients. They are then translocated through the outer membrane and transit through the periplasm by either the Tol or the TonB system. The components of each system are known, and their implication in the functioning of the system is described. Colicins then reach their lethal target and act either by forming a voltage-dependent channel into the inner membrane or by using their endonuclease activity on DNA, rRNA, or tRNA. The mechanisms of inhibition by specific and cognate immunity proteins are presented. Finally, the use of colicins as laboratory or biotechnological tools and their mode of evolution are discussed.
authors.affiliation: Laboratoire d'Ingénierie des Systèmes Macromoléculaires,Institut de Biologie Structurale et Microbiologie, Centre National de la Recherche Scientifique, UPR 9027, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France. cascales@ibsm.cnrs-mrs.fr
authors.forename: Eric
authors.initials: E
authors.lastname: Cascales
authors.forename: Susan K
authors.initials: SK
authors.lastname: Buchanan
authors.forename: Denis
authors.initials: D
authors.lastname: Duché
authors.forename: Colin
authors.initials: C
authors.lastname: Kleanthous
authors.forename: Roland
authors.initials: R
authors.lastname: Lloubès
authors.forename: Kathleen
authors.initials: K
authors.lastname: Postle
authors.forename: Margaret
authors.initials: M
authors.lastname: Riley
authors.forename: Stephen
authors.initials: S
authors.lastname: Slatin
authors.forename: Danièle
authors.initials: D
authors.lastname: Cavard
mesh_terms: D000595:Amino Acid Sequence; D003087:Colicins / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D021381:Protein Transport; D017386:Sequence Homology, Amino Acid
chemical_list: D003087:Colicins; D029968:Escherichia coli Proteins