title: Structure-activity analysis of an antimicrobial peptide derived from bovine apolipoprotein A-II.
abstract: We previously showed that bovine apolipoprotein A-II (apoA-II) has antimicrobial activity against Escherichia coli in PBS, and its C-terminal residues 49-76 are responsible for the activity using synthetic peptides. In order to understand the structural requirements of peptide 49-76 for the antimicrobial activity, the N- or C-terminus was truncated and then the charged (Lys or Asp) or Ser residues were replaced by Ala. Deletion of the first or last three amino acids and replacement of Lys-54/55 or 71/72 by Ala caused a substantial decreases in alpha-helical content in 50% TFE, showing the possible presence of helices in N- and C-terminal regions, respectively. The anti-Escherichia coli activity of the peptide correlated with its liposome-binding activity. Replacement of Lys-54/55 or 71/72 by Ala resulted in an almost complete loss of anti-E. coli activity with a substantial decrease in liposome-binding activity. Moreover, deletion of the last three amino acids caused a reduction to 1/17 of the original anti-E. coli activity with a moderate decrease in liposome-binding activity. In contrast, replacement of Ser-65/66, Asp-59, or Asp-69 by Ala hardly affected the anti-E. coli activity. These findings suggest that Lys-54/55 and Lys-71/72 on the putative helices are critical for antimicrobial activity, and the C-terminal 3 amino acids are important for the structural integrity of the C-terminal region for effective antimicrobial activity.
authors.affiliation: Department of Biochemistry Yamanashi Medical University, Nakakoma, Yamanashi 409-3898, Japan. mitsum@swallow.res.yamanashi-med.ac.jp
authors.forename: Mitsuyoshi
authors.initials: M
authors.lastname: Motizuki
authors.forename: Takanori
authors.initials: T
authors.lastname: Satoh
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Takei
authors.forename: Takehito
authors.initials: T
authors.lastname: Itoh
authors.forename: Sadaki
authors.initials: S
authors.lastname: Yokota
authors.forename: Shuichi
authors.initials: S
authors.lastname: Kojima
authors.forename: Kin-ichiro
authors.initials: K
authors.lastname: Miura
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Samejima
authors.forename: Kunio
authors.initials: K
authors.lastname: Tsurugi
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology*; D016633:Apolipoprotein A-II / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D002417:Cattle; D002942:Circular Dichroism; D004926:Escherichia coli / Q000166:cytology / Q000187:drug effects* / Q000648:ultrastructure; D020128:Inhibitory Concentration 50; D008081:Liposomes / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D010455:Peptides; D011485:Protein Binding; D017433:Protein Structure, Secondary; D013329:Structure-Activity Relationship
chemical_list: D000900:Anti-Bacterial Agents; D016633:Apolipoprotein A-II; D008081:Liposomes; D010455:Peptides