title: Structure-activity relationships of fowlicidin-1, a cathelicidin antimicrobial peptide in chicken.
abstract: Cationic antimicrobial peptides are naturally occurring antibiotics that are actively being explored as a new class of anti-infective agents. We recently identified three cathelicidin antimicrobial peptides from chicken, which have potent and broad-spectrum antibacterial activities in vitro (Xiao Y, Cai Y, Bommineni YR, Fernando SC, Prakash O, Gilliland SE & Zhang G (2006) J Biol Chem281, 2858-2867). Here we report that fowlicidin-1 mainly adopts an alpha-helical conformation with a slight kink induced by glycine close to the center, in addition to a short flexible unstructured region near the N terminus. To gain further insight into the structural requirements for function, a series of truncation and substitution mutants of fowlicidin-1 were synthesized and tested separately for their antibacterial, cytolytic and lipopolysaccharide (LPS)-binding activities. The short C-terminal helical segment after the kink, consisting of a stretch of eight amino acids (residues 16-23), was shown to be critically involved in all three functions, suggesting that this region may be required for the peptide to interact with LPS and lipid membranes and to permeabilize both prokaryotic and eukaryotic cells. We also identified a second segment, comprising three amino acids (residues 5-7) in the N-terminal flexible region, that participates in LPS binding and cytotoxicity but is less important in bacterial killing. The fowlicidin-1 analog, with deletion of the second N-terminal segment (residues 5-7), was found to retain substantial antibacterial potency with a significant reduction in cytotoxicity. Such a peptide analog may have considerable potential for development as an anti-infective agent.
authors.affiliation: Department of Animal Science, Oklahoma State University, Stillwater, OK 74078, USA.
authors.forename: Yanjing
authors.initials: Y
authors.lastname: Xiao
authors.forename: Huaien
authors.initials: H
authors.lastname: Dai
authors.forename: Yugendar R
authors.initials: YR
authors.lastname: Bommineni
authors.forename: Jose L
authors.initials: JL
authors.lastname: Soulages
authors.forename: Yu-Xi
authors.initials: YX
authors.lastname: Gong
authors.forename: Om
authors.initials: O
authors.lastname: Prakash
authors.forename: Guolong
authors.initials: G
authors.lastname: Zhang
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D001665:Binding Sites; D002478:Cells, Cultured; D002645:Chickens / Q000378:metabolism; D004285:Dogs; D006090:Gram-Negative Bacteria / Q000187:drug effects; D006094:Gram-Positive Bacteria / Q000187:drug effects; D006801:Humans; D008070:Lipopolysaccharides / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013329:Structure-Activity Relationship; D054804:Cathelicidins
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D008070:Lipopolysaccharides; D054804:Cathelicidins