Mechanism of Antibacterial Cationic Peptide caP4 from Curcuma pseudomontana L. (Zingiberaceae) Against E. coli

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Mechanism of Antibacterial Cationic Peptide caP4 from Curcuma pseudomontana L. (Zingiberaceae) Against E. coli Syeda Hajira Banu1 · Mukunda Chethan Kumar2  Accepted: 23 September 2020 © Springer Nature B.V. 2020

Abstract In our previous published article (https​://doi.org/10.1007/s1098​9-019-09883​-7), caP4—a cationic peptide of 2.97 kDa from Curcuma pseudomontana L. (Zingiberaceae) with sequences ASSCKPS and ASSKWVAPSEW showed significant antibacterial activity against Escherichia coli and Staphylococcus aureus. In the present study, circular dichroism (CD) data of caP4 showed 0% α-helix, 21.6% β-sheet, 31.2% β-turns, and 47.2% random coils. Further, the study was focused on understanding the mode of action of caP4 against E. coli. At 8 µg/ml (MIC), caP4 permeabilized the cell membrane with maximum recorded at 50 min. Scanning electron microscopy analysis of E. coli cells with caP4 at 16 µg/ml showed disorientation of the membrane surface. Cetyl pyridinium chloride (CPC, 10 µg/ml-IC50), Mitomycin C (10 µg/ml-IC50), Colchicine (25 µg/ ml-IC50), Cytochalasin B (30 µg/ml-IC50) and Cibacron blue (25 µg/ml-IC50) were used as cell growth inhibitors with or without caP4 (8 µg/ml) to check the action of peptide intracellularly. E. coli cells with caP4 showed 100% cell death at 100 min. E. coli cells pre-treated with caP4 for 30 min showed 100% and 96% cell death at 60 min and 56 min with CPC and Mitomycin C respectively, suggesting that caP4 is acting by entering into the cell membrane and thus inhibit protein synthesis similar to CPC and Mitomycin C, whereas Colchicine, Cytochalasin B, Cibacron blue did not show significant cell death with pre and post-treatment of caP4. Thus, the study showed the synergistic effect of caP4 with cell growth inhibitors CPC and Mitomycin C in enhancing the antibacterial activity. Thus the data provide a new insight to understand the mechanism of antibiotic activity of caP4 and could lay the foundation for developing plant based antibacterial drugs in future to combat drug resistant microbes. Keywords  Curcuma pseudomontana L. · Cationic antibacterial peptide · Mitomycin C · Cetyl Pyridinium Chloride · orthoNitrophenyl-β-galactoside

Introduction The technological advancements have lead to the identification and development of antimicrobial peptides (AMPs) as future therapeutics. Many of the synthetic and naturally occurring AMPs contain 10–55 amino acid residues with molecular weight ranging from 2 to 9 kDa (Robert et al. 2014). Many of the AMPs reported till date is cationic in nature exhibiting predominantly β-sheets and to lesser extent * Mukunda Chethan Kumar [email protected] 1



JSS Research Foundation, SJCE Technical Institution Campus, Mysuru, Karnataka 570006, India



JSS College of Arts, Commerce and Science (Affiliated to University of Mysore), Ooty Road, Mysuru, Karnataka 570025, India

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α-helices with looped and extended structures or with a combination of these structures (Rajeshwari and Pratyoosh 2019; Meri et al. 2019). Indolicin, a 13-residue cationic, antimi