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ACS Infect Dis. 2019 Jul 12;5(7):1200-1213. doi: 10.1021/acsinfecdis.9b00042. Epub 2019 May 10.

Enhanced Silkworm Cecropin B Antimicrobial Activity against Pseudomonas aeruginosa from Single Amino Acid Variation.

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Department of Biology , University of Padova , Via Ugo Bassi 58/B , 35131 Padova , Italy.
Department of Biophysics , Bose Institute , P-1/12 CIT Scheme VII (M) , 700 054 Kolkata , India.
Department of Chemistry , Bose Institute , 93/1 A P C Road , 700 009 Kolkata , India.
Department of Biotechnology and Life Sciences , University of Insubria , Via Jean Henry Dunant, 3 , 21100 Varese , Italy.
Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, Institut de Biologie Physico-Chimique, CNRS, UMR7099 , University Paris Diderot, Sorbonne Paris Cité, Paris Sciences et Lettres Research University , F-75005 Paris , France.


Pseudomonas aeruginosa is an opportunistic bacterial pathogen causing severe infections in hospitalized and immunosuppressed patients, particularly individuals affected by cystic fibrosis. Several clinically isolated P. aeruginosa strains were found to be resistant to three or more antimicrobial classes indicating the importance of identifying new antimicrobials active against this pathogen. Here, we characterized the antimicrobial activity and the action mechanisms against P. aeruginosa of two natural isoforms of the antimicrobial peptide cecropin B, both isolated from the silkworm Bombyx mori. These cecropin B isoforms differ in a single amino acid substitution within the active portion of the peptide, so that the glutamic acid of the E53 CecB variant is replaced by a glutamine in the Q53 CecB isoform. Both peptides showed a high antimicrobial and membranolytic activity against P. aeruginosa, with Q53 CecB displaying greater activity compared with the E53 CecB isoform. Biophysical analyses, live-cell NMR, and molecular-dynamic-simulation studies indicated that both peptides might act as membrane-interacting elements, which can disrupt outer-membrane organization, facilitating their translocation toward the inner membrane of the bacterial cell. Our data also suggest that the amino acid variation of the Q53 CecB isoform represents a critical factor in stabilizing the hydrophobic segment that interacts with the bacterial membrane, determining the highest antimicrobial activity of the whole peptide. Its high stability to pH and temperature variations, tolerance to high salt concentrations, and low toxicity against human cells make Q53 CecB a promising candidate in the development of CecB-derived compounds against P. aeruginosa.


; NMR; antimicrobial peptides; cecropin B

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