We previously showed that bovine apolipoprotein A-II (apoA-II) had antimicrobial activity against Escherichia coli and the yeast Saccharomyces cerevisiae in PBS. We have characterized here the active domain of apoA-II using synthetic peptides. A peptide corresponding to C-terminal residues Leu49-Thr76 exhibited significant antimicrobial activity against E. coli in PBS, but not against S. cerevisiae. Experiments using amino-acid-substituted peptides indicated that the residues Phe52-Phe53-Lys54-Lys55 are required for the activity. Peptide Leu49-Thr76 induced the release of calcein trapped inside the vesicles whose lipid composition resembles that of E. coli membrane, suggesting that peptide Leu49-Thr76 can destabilize the E. coli membrane. CD measurements showed that the α-helicity of peptide Leu49-Thr76 increased from 3.5 to 36% by addition of the vesicles. When E. coli cells were incubated with peptide Leu49-Thr76, some proteins were released to the external medium, probably owing to membrane destabilization caused by the peptide. In electron micrographs of E. coli cells treated with peptide Leu49-Thr76, transparent nucleoids and granulated cytoplasm were observed. Amino acid substitutions, Phe52Phe53 → AlaAla (Phe52,53 → Ala) in peptide Leu49-Thr76 caused the loss of antimicrobial activity against E. coli, although protein-releasing activity was retained. Electron micrographs of the cells treated with peptide Leu49-Thr76(Phe52,53 → Ala) revealed morphological change only at the nucleoids. Therefore peptide Leu49-Thr76 appears to primarily target the cytoplasm rather than the membrane of E. coli cells.
Lipid-binding and antimicrobial properties of synthetic peptides of bovine apolipoprotein A-II
- Views Icon Views
- Share Icon Share
- Cite Icon Cite
Mitsuyoshi MOTIZUKI, Takehito ITOH, Takanori SATOH, Sadaki YOKOTA, Muneo YAMADA, Seiichi SHIMAMURA, Tatsuya SAMEJIMA, Kunio TSURUGI; Lipid-binding and antimicrobial properties of synthetic peptides of bovine apolipoprotein A-II. Biochem J 15 August 1999; 342 (1): 215–221. doi: https://doi.org/10.1042/bj3420215
Download citation file: