Journal of Biological Chemistry
Volume 283, Issue 37, 12 September 2008, Pages 25589-25595
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Protein Synthesis, Post-Translational Modification, and Degradation
Systematic Structure-Activity Analysis of Microcin J25*

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Microcin J25 (MccJ25) is a 21-residue plasmid-encoded ribosomally synthesized lariat-protoknot antibacterial peptide that targets bacterial RNA polymerase. MccJ25 consists of an 8-residue cycle followed by a 13-residue tail that loops back and threads through the cycle. We have performed systematic mutational scanning of MccJ25, constructing and analyzing more than 380 singly substituted derivatives of MccJ25. The results define residues important for production of MccJ25 (comprising synthesis of MccJ25 precursor, processing of MccJ25 precursor, export of mature MccJ25, and stability of mature MccJ25), inhibition of RNA polymerase, and inhibition of bacterial growth. The results show that only a small number of residues (three in the cycle and one in the threaded segment of the tail) are important for MccJ25 production. The results further show that only a small number of additional residues (two in the cycle and four in the threaded segment of the tail) are important for inhibition of transcription. The results open the way for design and construction of more potent MccJ25-based inhibitors of bacterial growth.

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This work was supported, in whole or in part, by National Institutes of Health Grants GM41376 (to R. H. E.) and GM64530 (to K. S.) and by a NIAID North-east Biodefense center U54-AI057158-Lipkin Grant (to K. S.). This work was also supported by a Howard Hughes Medical Institute Investigatorship (to R. H. E.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.