title: Pseudomonas syringae self-protection from tabtoxinine-β-lactam by ligase TblF and acetylase Ttr.
abstract: Plant pathogenic Pseudomonas syringae produce the hydroxy-β-lactam antimetabolite tabtoxinine-β-lactam (TβL) as a time-dependent inactivating glutamine analogue of plant glutamine synthetases. The producing pseudomonads use multiple modes of self-protection, two of which are characterized in this study. The first is the dipeptide ligase TblF which converts tabtoxinine-β-lactam to the TβL-Thr dipeptide known as tabtoxin. The dipeptide is not recognized by glutamine synthetase. This represents a Trojan Horse strategy: the dipeptide is secreted, taken up by dipeptide permeases in neighboring cells, and TβL is released by peptidase action. The second self-protection mode is elaboration by the acetyltransferase Ttr, which acetylates the α-amino group of the proximal inactivator TβL, but not the tabtoxin dipeptide.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, United States.
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Wencewicz
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Walsh
mesh_terms: D000123:Acetyltransferases / Q000378:metabolism*; D001384:Azetidines / Q000378:metabolism*; D001427:Bacterial Toxins / Q000378:metabolism*; D004151:Dipeptides / Q000378:metabolism*; D008025:Ligases / Q000378:metabolism*; D010944:Plants / Q000382:microbiology; D044224:Pseudomonas syringae / Q000201:enzymology* / Q000378:metabolism; D013912:Threonine / Q000378:metabolism
chemical_list: D001384:Azetidines; D001427:Bacterial Toxins; D004151:Dipeptides; D013912:Threonine; C051368:tabtoxinine beta-lactam; D000123:Acetyltransferases; D008025:Ligases; C003854:tabtoxin