title: Structural characterization of antibiotic self-immunity tRNA synthetase in plant tumour biocontrol agent.
abstract: Antibiotic-producing microbes evolved self-resistance mechanisms to avoid suicide. The biocontrol Agrobacterium radiobacter K84 secretes the Trojan Horse antibiotic agrocin 84 that is selectively transported into the plant pathogen A. tumefaciens and processed into the toxin TM84. We previously showed that TM84 employs a unique tRNA-dependent mechanism to inhibit leucyl-tRNA synthetase (LeuRS), while the TM84-producer prevents self-poisoning by expressing a resistant LeuRS AgnB2. We now identify a mechanism by which the antibiotic-producing microbe resists its own toxin. Using a combination of structural, biochemical and biophysical approaches, we show that AgnB2 evolved structural changes so as to resist the antibiotic by eliminating the tRNA-dependence of TM84 binding. Mutagenesis of key resistance determinants results in mutants adopting an antibiotic-sensitive phenotype. This study illuminates the evolution of resistance in self-immunity genes and provides mechanistic insights into a fascinating tRNA-dependent antibiotic with applications for the development of anti-infectives and the prevention of biocontrol emasculation.
authors.affiliation: Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7090, USA.
authors.forename: Shaileja
authors.initials: S
authors.lastname: Chopra
authors.affiliation: European Molecular Biology Laboratory, Grenoble Outstation and Unit of Virus Host-Cell Interactions, UJF-EMBL-CNRS, UMI 3265, 71, Avenue des Martyrs, CS 90181, 38042 Grenoble Cedex 96 rue Jules Horowitz, BP181, Grenoble Cedex 9 38042, France.
authors.forename: Andrés
authors.initials: A
authors.lastname: Palencia
authors.affiliation: Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7090, USA.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Virus
authors.affiliation: Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7090, USA.
authors.forename: Sarah
authors.initials: S
authors.lastname: Schulwitz
authors.affiliation: R.L. Juliano Structural Bioinformatics Core Facility, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
authors.forename: Brenda R
authors.initials: BR
authors.lastname: Temple
authors.affiliation: European Molecular Biology Laboratory, Grenoble Outstation and Unit of Virus Host-Cell Interactions, UJF-EMBL-CNRS, UMI 3265, 71, Avenue des Martyrs, CS 90181, 38042 Grenoble Cedex 96 rue Jules Horowitz, BP181, Grenoble Cedex 9 38042, France.
authors.forename: Stephen
authors.initials: S
authors.lastname: Cusack
authors.affiliation: Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7090, USA.
authors.forename: John
authors.initials: J
authors.lastname: Reader
mesh_terms: D016960:Agrobacterium tumefaciens / Q000235:genetics*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D019143:Evolution, Molecular; D005798:Genes, Bacterial; D007700:Kinetics; D007935:Leucine-tRNA Ligase / Q000037:antagonists & inhibitors* / Q000235:genetics* / Q000378:metabolism; D010572:Pest Control, Biological; D010941:Plant Tumors / Q000382:microbiology; D012343:RNA, Transfer / Q000378:metabolism
chemical_list: D012343:RNA, Transfer; D007935:Leucine-tRNA Ligase