title: Structural and functional analysis of the kid toxin protein from E. coli plasmid R1.
abstract: We have determined the structure of Kid toxin protein from E. coli plasmid R1 involved in stable plasmid inheritance by postsegregational killing of plasmid-less daughter cells. Kid forms a two-component system with its antagonist, Kis antitoxin. Our 1.4 A crystal structure of Kid reveals a 2-fold symmetric dimer that closely resembles the DNA gyrase-inhibitory toxin protein CcdB from E. coli F plasmid despite the lack of any notable sequence similarity. Analysis of nontoxic mutants of Kid suggests a target interaction interface associated with toxicity that is in marked contrast to that proposed for CcdB. A possible region for interaction of Kid with the antitoxin is proposed that overlaps with the target binding site and may explain the mode of antitoxin action.
authors.affiliation: Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Hargreaves
authors.forename: Sandra
authors.initials: S
authors.lastname: Santos-Sierra
authors.forename: Rafael
authors.initials: R
authors.lastname: Giraldo
authors.forename: Rosario
authors.initials: R
authors.lastname: Sabariegos-Jareño
authors.forename: Guillermo
authors.initials: G
authors.lastname: de la Cueva-Méndez
authors.forename: Rolf
authors.initials: R
authors.lastname: Boelens
authors.forename: Ramon
authors.initials: R
authors.lastname: Díaz-Orejas
authors.forename: John B
authors.initials: JB
authors.lastname: Rafferty
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000494:pharmacology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010957:Plasmids; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid
chemical_list: D029968:Escherichia coli Proteins; C473072:kid toxin protein, E coli plasmid R1