Novel Variants of Microcin J25 with Increased Potency against Gram Negative Bacteria

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Princeton Docket # 11-2663


Researchers at Princeton University created novel peptide derivatives of the antimicrobial peptide Microcin J25 (MccJ25) with multiple amino acid substitutions and potent activity against Gram-negative bacteria. The most potent MccJ25 variants displayed up to a nearly 5-fold improvement in bacterial growth inhibition action against E. coli and the pathogenic Salmonella strain S. Newport.


Few new classes of antibiotics have been discovered in the past decades and the emergence of multi-drug resistant organisms demands new antibiotics to treat infections.  MccJ25 is a promising new candidate for antimicrobial use because of its potent mechanism of action by inhibiting bacterial RNA polymerase. The MccJ25 derivatives described here have been isolated by genetic modification and have higher potency than the wild-type antibiotic. Unlike the cationic antimicrobial peptides, MccJ25 derivatives can be produced in high yield in bacterial hosts and are extremely stable in conditions of extreme temperature or chemical denaturation due to the threaded lasso structure.


Besides the application as an antimicrobial therapeutic, the MccJ25 derivatives also hold the promise to be the next-generation food preservative.  Nisin, a polycyclic antibacterial peptide, is widely used as a food preservative for its suppression of gram-positive spoilage and pathogenic bacteria.  However, it is not effective against Gram-negative bacteria, yeast or moulds.  The stability of nisin during storage is dependent upon incubation temperature, length of storage and pH.  A typical cheese pasteurization process (85¿105°C for 5¿10 min at pH 5.6¿5.8) results in 20-30% loss of activity, and storage at 25 °C for 30 weeks leads to 40% loss.  In addition, nisin is usually naturally produced from Streptococcus lactis cultured on milk, and thus may not be safe to be used by people with an allergy to milk protein or with lactose intolerance.  The MccJ25 derivatives, with high thermal stability and specificity against gram-negative bacteria, are anticipated to be a better antimicrobial food preservative. 



·         Antimicrobial therapeutic

·         Food preservative



·         5-fold improvement in bacterial growth inhibition

·         Exceptional stability towards thermal, and chemical denaturation

·         Proteases Resistance

·         Ability to expand SAR on MccJ25



Pan SJ, Link AJ, (2011) Sequence Diversity in the Lasso Peptide Framework: Discovery of Functional Microcin J25 Variants with Multiple Amino Acid Substitutions. J Am Chem Soc. 133 (13), pp 5016-5023.


Faculty Inventor

A. James Link is assistant professor of chemical and biological engineering in the department of chemical and biological engineering, at Princeton University. The research in his group is highly interdisciplinary and focuses on protein engineering and chemical biology. One of the major focuses of his group is to apply directed evolution to medically relevant proteins.


Intellectual Property status

Patent protection is pending.

Patent Information:
For Information, Contact:
Laurie Tzodikov
Licensing Associates
Princeton University
Aaron James Link
Si Jia Pan
drug discovery
platform technology