title: Microcin J25 uptake: His5 of the MccJ25 lariat ring is involved in interaction with the inner membrane MccJ25 transporter protein SbmA.
abstract: Escherichia coli microcin J25 (MccJ25) is a plasmid-encoded antibiotic peptide consisting of 21 L-amino acid residues (G1-G-A-G-H5-V-P-E-Y-F10-V-G-I-G-T15-P-I-S-F-Y20-G). E. coli RNA polymerase (RNAP) is the intracellular target of MccJ25. MccJ25 enters cells after binding to specific membrane transporters: FhuA in the outer membrane and SbmA in the inner membrane. Here, we studied MccJ25 mutants carrying a substitution of His5 by Lys, Arg, or Ala. The inhibitory effects on cellular growth and in vitro RNAP activity were determined for each mutant microcin. The results show that all mutants inhibited RNAP in vitro. However, the mutants were defective in their ability to inhibit cellular growth. Experiments in which the FhuA protein was bypassed showed that substitutions of MccJ25 His5 affected the SbmA-dependent transport. Our results thus suggest that MccJ25 His5 located in the lariat ring is involved, directly or indirectly, in specific interaction with SbmA and is not required for MccJ25 inhibition of RNAP.
authors.affiliation: Departamento de Bioquímica de la Nutrición, Instituto Superior de Investigaciones Biológicas (Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de Tucumán), San Miguel de Tucumán, Argentina.
authors.forename: Ricardo E
authors.initials: RE
authors.lastname: de Cristóbal
authors.forename: Jose O
authors.initials: JO
authors.lastname: Solbiati
authors.forename: Ana M
authors.initials: AM
authors.lastname: Zenoff
authors.forename: Paula A
authors.initials: PA
authors.lastname: Vincent
authors.forename: Raul A
authors.initials: RA
authors.lastname: Salomón
authors.forename: Julia
authors.initials: J
authors.lastname: Yuzenkova
authors.forename: Konstantin
authors.initials: K
authors.lastname: Severinov
authors.forename: Ricardo N
authors.initials: RN
authors.lastname: Farías
mesh_terms: D019943:Amino Acid Substitution; D000900:Anti-Bacterial Agents / Q000378:metabolism* / Q000494:pharmacology; D001430:Bacteriocins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D001692:Biological Transport; D012321:DNA-Directed RNA Polymerases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D006639:Histidine / Q000235:genetics / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism*; D009154:Mutation; D012329:RNA, Bacterial / Q000096:biosynthesis
chemical_list: D000900:Anti-Bacterial Agents; D001430:Bacteriocins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D012329:RNA, Bacterial; C020411:microcin; D006639:Histidine; D012321:DNA-Directed RNA Polymerases