title: Comparative mode of action of novel hybrid peptide CS-1a and its rearranged amphipathic analogue CS-2a.
abstract: Cell selective, naturally occurring, host defence cationic peptides present a good template for the design of novel peptides with the aim of achieving a short length with improved antimicrobial potency and selectivity. A novel, short peptide CS-1a (14 residues) was derived using a sequence hybridization approach on sarcotoxin I (39 residues) and cecropin B (35 residues). The sequence of CS-1a was rearranged to enhance amphipathicity with the help of a Schiffer-Edmundson diagram to obtain CS-2a. Both peptides showed good antibacterial activity in the concentration range 4-16 μg·mL(-1) against susceptible as well as drug-resistant bacterial strains, including the clinically relevant pathogens Acenatobacter sp. and methicillin-resistant Staphylococcus aureus. The major thrust of these peptides is their nonhaemolytic activity against human red blood cells up to a high concentration of 512 μg·mL(-1). Compared to CS-1a, amphipathic peptide CS-2a showed a more pronounced α-helical conformation, along with a better membrane insertion depth in bacterial mimic 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) small unilamellar vesicles. With equivalent lipid-binding affinity, the two peptides assumed different pathways of membrane disruption, as demonstrated by calcein leakage and the results of transmission electron microscopy on model bacterial mimic large unilamellar vesicles. Extending the work from model membranes to intact Escherichia coli cells, differences in membrane perturbation were visible in microscopic images of peptide-treated E. coli. The present study describes two novel short peptides with potent activity, cell selectivity and divergent modes of action that will aid in the future design of peptides with better therapeutic potential.
authors.affiliation: Peptide Research Laboratory, Institute of Genomics & Integrative Biology, Delhi, India.
authors.forename: Seema
authors.initials: S
authors.lastname: Joshi
authors.forename: Gopal S
authors.initials: GS
authors.lastname: Bisht
authors.forename: Diwan S
authors.initials: DS
authors.lastname: Rawat
authors.forename: Souvik
authors.initials: S
authors.lastname: Maiti
authors.forename: Santosh
authors.initials: S
authors.lastname: Pasha
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects*; D002942:Circular Dichroism; D004926:Escherichia coli / Q000737:chemistry / Q000187:drug effects / Q000648:ultrastructure; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D019476:Insect Proteins / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D044007:Moraxellaceae / Q000187:drug effects; D010455:Peptides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D010715:Phosphatidylglycerols / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D053835:Unilamellar Liposomes / Q000737:chemistry / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D019476:Insect Proteins; D008051:Lipid Bilayers; D010455:Peptides; D010715:Phosphatidylglycerols; D053835:Unilamellar Liposomes; D015060:1,2-Dipalmitoylphosphatidylcholine; C081581:colfosceril palmitate; C031162:cecropin B protein, Insecta; C042572:sarcotoxin I protein, Sarcophaga peregrina; C030345:1,2-dipalmitoylphosphatidylglycerol