title: Cysteine deleted protegrin-1 (CDP-1): anti-bacterial activity, outer-membrane disruption and selectivity.
abstract: BACKGROUND
  Protegin-1 (PG-1: RGGRLCYCRRRFCVCVGR-amide) assumes a rigid β-hairpin like structure that is stabilized by two disulfide bridges between Cys6-Cys15 and Cys8-Cys13. Previous studies, employing linear analogs of PG-1, with Cys to Ala mutations or modified Cys, have demonstrated that the disulfide bridges are critical for the broad spectrum and salt resistant antimicrobial activity of PG-1.
  
  
  METHODS
  In order to understand structural and functional roles of disulfide bonds in protegrins, we have synthesized a Cys deleted variant of PG-1 or CDP-1, RGGRLYRRRFVVGR-amide, and two of its analogs, RR11, RLYRRRFVVGR-amide, and LR10, LYRRRFVVGR-amide, containing deletion of residues at the N-terminus. These peptides have been characterized for bactericidal activity and mode of action in lipopolysaccharide (LPS) using optical spectroscopy, ITC and NMR.
  
  
  RESULTS
  Antibacterial activity, against Gram-negative and Gram-positive strains, of the three peptides follows the order: CDP-1>RR11>LR10. LR10 displays only limited activity toward Gram-negative strains. CDP-1 demonstrates efficient membrane permeabilization and high-affinity interactions with LPS. CDP-1 and RR11 both assume β-hairpin like compact structures in complex with LPS, whereas LR10 adopts an extended conformation in LPS. In zwitterionic DPC micelles CDP-1 and the truncated analog peptides do not adopt folded conformations.
  
  
  CONCLUSIONS
  Despite the absence of stabilizing disulfide bridges CDP-1 shows broad-spectrum antibacterial activity and assumes β-hairpin like structure in complex with LPS. The β-hairpin structure may be essential for outer membrane permeabilization and cell killing.
authors.affiliation: School of Biological Sciences, Structural Biology and Biochemistry, Nanyang Technological University, 637551, Singapore.
authors.forename: Harini
authors.initials: H
authors.lastname: Mohanram
authors.affiliation: School of Biological Sciences, Structural Biology and Biochemistry, Nanyang Technological University, 637551, Singapore. Electronic address: surajit@ntu.edu.sg.
authors.forename: Surajit
authors.initials: S
authors.lastname: Bhattacharjya
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000493:pharmacokinetics; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry* / Q000235:genetics / Q000493:pharmacokinetics; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism; D002463:Cell Membrane Permeability; D006090:Gram-Negative Bacteria / Q000737:chemistry* / Q000378:metabolism; D006094:Gram-Positive Bacteria / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism; D017433:Protein Structure, Secondary
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D008070:Lipopolysaccharides; C094880:protegrin-1
keywords: Antibiotics; Antimicrobial peptides; Lipopolysaccharide; NMR; Protegrin-1