This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by de Cristóbal, R. E. Articles by Farías, R. N. Search for Related Content PubMed PubMed Citation Articles by de Cristóbal, R. E. Articles by Farías, R. N.

Microcin J25 Uptake: His⁵ of the MccJ25 Lariat Ring Is Involved in Interaction with the Inner Membrane MccJ25 Transporter Protein SbmA

Departamento de Bioquímica de la Nutrición, Instituto Superior de Investigaciones Biológicas (Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de Tucumán), Chacabuco 461, 4000 San Miguel de Tucumán, Tucumán, Argentina,¹ Department of Molecular Biology and Biochemistry, Waksman Institute, Piscataway, New Jersey 08854²

Received 15 December 2005/ Accepted 22 February 2006

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.