title: Structure of antibacterial peptide microcin J25: a 21-residue lariat protoknot.
abstract: The antibacterial peptide microcin J25 (MccJ25) inhibits bacterial transcription by binding within, and obstructing, the nucleotide-uptake channel of bacterial RNA polymerase. Published covalent and three-dimensional structures indicate that MccJ25 is a 21-residue cycle. Here, we show that the published covalent and three-dimensional structures are incorrect, and that MccJ25 in fact is a 21-residue "lariat protoknot", consisting of an 8-residue cyclic segment followed by a 13-residue linear segment that loops back and threads through the cyclic segment. MccJ25 is the first example of a lariat protoknot involving a backbone-side chain amide linkage.
authors.affiliation: Department of Molecular Biology and Biochemistry, Waksman Institute, and Howard Hughes Medical Institute, Rutgers University, Piscataway, New Jersey 08854, USA.
authors.forename: Marvin J
authors.initials: MJ
authors.lastname: Bayro
authors.forename: Jayanta
authors.initials: J
authors.lastname: Mukhopadhyay
authors.forename: G V T
authors.initials: GV
authors.lastname: Swapna
authors.forename: Janet Y
authors.initials: JY
authors.lastname: Huang
authors.forename: Li-Chung
authors.initials: LC
authors.lastname: Ma
authors.forename: Elena
authors.initials: E
authors.lastname: Sineva
authors.forename: Philip E
authors.initials: PE
authors.lastname: Dawson
authors.forename: Gaetano T
authors.initials: GT
authors.lastname: Montelione
authors.forename: Richard H
authors.initials: RH
authors.lastname: Ebright
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry; D001430:Bacteriocins / Q000737:chemistry*; D008958:Models, Molecular; D010455:Peptides; D011487:Protein Conformation; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D000900:Anti-Bacterial Agents; D001430:Bacteriocins; D010455:Peptides; C020411:microcin