title: Interaction studies of novel cell selective antimicrobial peptides with model membranes and E. coli ATCC 11775.
abstract: Cationic antimicrobial peptides (CAMPs) are novel candidates for drug development. Here we describe design of six short and potent CAMPs (SA-1 to SA-6) based on a minimalist template of 12 residues H+HHG+HH+HH+NH2 (where H: hydrophobic amino acid and +: charged hydrophilic amino acid). Designed peptides exhibit good antibacterial activity in micro molar concentration range (1-32 mug/ml) and rapid clearance of Gram-positive and Gram-negative bacterial strains at concentrations higher than MIC. For elucidating mode of action of designed peptides various biophysical studies including CD and Trp fluorescence were performed using model membranes. Further based on activity, selectivity and membrane bound structure; modes of action of Trp rich peptide SA-3 and template based peptide SA-4 were compared. Calcein dye leakage and transmission electron microscopic studies with model membranes exhibited selective membrane active mode of action for peptide SA-3 and SA-4. Extending our work from model membranes to intact E. coli ATCC 11775 in scanning electron micrographs we could visualize different patterns of surface perturbation caused by peptide SA-3 and SA-4. Further at low concentration rapid translocation of FITC-tagged peptide SA-3 into the cytoplasm of E. coli cells without concomitant membrane perturbation indicates involvement of intracellular targeting mechanism as an alternate mode of action as was also evidenced in DNA retardation assay. For peptide SA-4 concentration dependent translocation into the bacterial cytoplasm along with membrane perturbation was observed. Establishment of a non specific membrane lytic mode of action of these peptides makes them suitable candidates for drug development.
authors.affiliation: Peptide Research Laboratory, Institute of Genomics and Integrative Biology, Mall Road, Delhi, India.
authors.forename: Seema
authors.initials: S
authors.lastname: Joshi
authors.forename: Gopal Singh
authors.initials: GS
authors.lastname: Bisht
authors.forename: Diwan S
authors.initials: DS
authors.lastname: Rawat
authors.forename: Anil
authors.initials: A
authors.lastname: Kumar
authors.forename: Rita
authors.initials: R
authors.lastname: Kumar
authors.forename: Souvik
authors.initials: S
authors.lastname: Maiti
authors.forename: Santosh
authors.initials: S
authors.lastname: Pasha
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D002417:Cattle; D002942:Circular Dichroism; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000378:metabolism; D006094:Gram-Positive Bacteria / Q000187:drug effects / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D010455:Peptides / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding
chemical_list: D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; D008051:Lipid Bilayers; D010455:Peptides; C073143:indolicidin