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© 2018 Elsevier B.V. All rights reserved., Antimicrobial peptides (AMPs) are promising candidates for the development of future antibiotics. In an attempt to increase the efficacy of therapeutic AMPs, computer-based design methods appear as a reliable strategy. In this study, we evaluated the antimicrobial efficiency and mechanism of action of a novel designed AMP named PaDBS1R1, previously designed by means of the Joker algorithm, using a fragment of the ribosomal protein L39E from the archaeon Pyrobaculum aerophilum as a template. PaDBS1R1 displayed low micromolar broad-spectrum antimicrobial activity against Gram-negative (MIC of 1.5 μM) and Gram-positive (MIC of 3 μM) bacteria, including carbapenem-resistant Klebsiella pneumoniae (MIC of 6.25 μM) and methicillin-resistant Staphylococcus aureus (MIC of 12.5 μM), without cytotoxicity towards HEK-293 cells. In addition, membrane permeabilization and depolarization assays, combined with time-kill studies and FEG-SEM imaging, indicated a fast membrane permeation and further leakage of intracellular content. Biophysical studies with lipid vesicles show a preference of PaDBS1R1 for Gram-negative bacteria-like membranes. We investigated the three-dimensional structure of PaDBS1R1 by CD and NMR analyses. Our results suggest that PaDBS1R1 adopts an amphipathic α-helix upon interacting with hydrophobic environments, after an initial electrostatic interaction with negative charges, suggesting a membrane lytic effect. This study reveals that PaDBS1R1 has potential application in antibiotic therapy., The authors acknowledge Fundação para a Ciência e a Tecnologia – Ministério da Ciência, Tecnologia e Ensino Superior (FCT-MCTES, Portugal) for funding, including fellowship SFRH/BD/100517/2014 to M.R.F., Marie Sklodowska-Curie Research and Innovation Staff Exchange (MSCA-RISE, European Union) project INPACT (call H2020-MSCA-RISE-2014, grant agreement 644167), IMPC (Institut des Matériaux de Paris Centre, FR 2482) and the C'Nano projects of the Region Ile-de-France for SEM-FEG funding. Conselho Nacional de Desenvolvimento Científico e Tecnológico – CNPq for financial support and researcher fellowship (Processes: 141327/2012-0; 407181/2013-0; 303181/20150), Coordenação de Aperfeiçoamento de Pessoal do Nível Superior – CAPES, for scholarship (Process: BEX 2758/15-6), and Fundação de Amparo à Pesquisa do Estado de Goiás – FAPEG (Process: 201710267000062). This work was also supported by Fundação de Amparo a Pesquisa do Mato Grosso do Sul (FUNDECT) and Fundação de Amapro a Pesquisa do Distrito Federal (FAPDF).

Plants are extensively used in traditional medicine, and several plant antimicrobial peptides have been described as potential alternatives to conventional antibiotics. However, after more than four decades of research no plant antimicrobial peptide is currently used for treating bacterial infections, due to their length, post-translational modifications or high dose requirement for a therapeutic effect . Here we report the design of antimicrobial peptides derived from a guava glycine-rich peptide using a genetic algorithm. This approach yields guavanin peptides, arginine-rich α-helical peptides that possess an unusual hydrophobic counterpart mainly composed of tyrosine residues. Guavanin 2 is characterized as a prototype peptide in terms of structure and activity. Nuclear magnetic resonance analysis indicates that the peptide adopts an α-helical structure in hydrophobic environments. Guavanin 2 is bactericidal at low concentrations, causing membrane disruption and triggering hyperpolarization. This computational approach for the exploration of natural products could be used to design effective peptide antibiotics., Antimicrobial peptides are considered promising alternatives to antibiotics. Here the authors developed a computational algorithm that starts with peptides naturally occurring in plants and optimizes this starting material to yield new variants which are highly distinct from the parent peptide.