Mapping of Apidaecin Regions Relevant for Antimicrobial Activity and Bacterial Internalization
- 183 Downloads
Apidaecins are 18–20-residue long proline-rich peptides expressed in insects as part of the innate immune system. They are very active against Gram-negative bacteria, especially Enterobacteriaceae. The C-terminal sequence PRPPHPRL is highly conserved, whereas the N-terminal region is variable. By replacing all 18 residues of apidaecin 1a and apidaecin 1b individually by alanine (Ala-scan), we have shown that single mutations in the C-terminal half of the peptides drastically reduced and mostly abolished the antibacterial activity against Escherichia coli. Conversely, substitutions in the N-terminal eight residues produced no, or only minor effects. The activity loss was correlated to the ability of apidaecin 1b and its mutants to enter Gram-negative bacteria, most likely because they no longer bind to a protein transporter. This assumed binding, however, was not inhibited by truncated apidaecin peptides added at tenfold higher concentrations. Interestingly, the antibacterial activity of full length apidaecin 1b was enhanced about four times by addition of a N-terminally truncated apidaecin peptide [11–18]-apidaecin 1b, as indicated by lower MIC-values against E. coli, although the short 5(6)-carboxyfluorescein-labeled peptide did not enter the bacteria. In contrast, the activity against the Gram-positive bacterium Micrococcus luteus was not located in the C-terminal sequence of apidaecins 1a and b, but depended mostly on the presence of all four basic residues.
KeywordsAlanine-scan Antibacterial peptide Escherichia coli Solid phase peptide synthesis Minimal inhibitory concentration
We thank Prof. Peter Seibel and Mr. Ingo Schäfer for recording the confocal microscope images. This work was supported by the European Fund for Regional Structure Development (EFRE, European Union and Free State Saxony).
- Amato-Gauci A, Ammon A (2007) The First European Communicable Disease Epidemiological Report. European Centre for Disease prevention and Control. ISBN 978 92-9193-062-3Google Scholar
- Cassone M, Frith N, Vogiatzi P, Wade JD, Otvos L (2009) Induced resistance to the designer proline-rich antimicrobial peptide A3-APO does not involve changes in the intracellular target DnaK. Int J Pept Res Ther. doi: 10.1007/s10989-009-9176-1
- Otvos L Jr, Bokonyi K, Varga I, Otvos BI, Hoffmann R, Ertl HC, Wade JD, McManus AM, Craik DJ, Bulet P (2000a) Insect peptides with improved protease-resistance protect mice against bacterial infection. Prot Sci 9:742Google Scholar
- Piantavigna S, Czihal P, Mechler A, Richter M, Hoffmann R, Martin LL (2009) Cell penetrating apidaecin peptides exhibit thresholded interactions with biomimetic phospholipid membranes. Int J Pept Res Ther. doi: 10.1007/s10989-009-9175-2
- Scocchi M, Lüthy C, Decarli P, Mignogna G, Christen P, Gennaro R (2009) The proline-rich antibacterial peptide Bac7 binds to and inhibits in vitro the molecular chaperone DnaK. Int J Pept Res Ther (this issue)Google Scholar