Apidaecin IB – Antimicrobial peptide
Apidaecin IB is a proline-rich antimicrobial peptide (PrAMP) isolated from Apis mellifera hemolymph. Apidaecin IB mainly possesses activity against Gram-negative bacteria. It has been reported that Apidaecin IB is a non-lytic AMP which enters the cell and inhibits an intracellular target, the chaperone DnaK. Apidaecin IB is not toxic for humans and animals. It has been studied for treating systemic bacterial infections.
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1- Gobbo M et al. J Med Chem (2002)
Antimicrobial peptides: synthesis and antibacterial activity of linear and cyclic drosocin and apidaecin 1b analogues.
BACKGROUND: Drosocin and apidaecin Ib are two insect antimicrobial peptides showing a significant sequence homology and a common mechanism of action, which includes stereoselective elements but is devoid of any pore-forming activity. A substantial difference between the two peptides is the presence in the drosocin sequence of an O-glycosylated threonine residue, which is important for its antimicrobial activity.
OBJECTIVE: Showing the antibacterial activity of Apidaecin Ib
METHOD/RESULTS: Through the synthesis of a series of differently glycosylated drosocin analogues, we have shown that the antimicrobial activity against several Gram-negative bacteria appears to be modulated by the sugar moiety (Gal vs GalNAc) and the type of glycosidic linkage (alpha-O-, beta-O-, or alpha-C-). The insertion of a glycosylated threonine residue in the apidaecin Ib sequence improves the sequence homology with drosocin but reduces the antimicrobial activity. To gain information on the possible bioactive conformation of these peptides, we synthesized an unglycosylated cyclic analogue of drosocin, containing an intrachain disulfide bond, and the head-to-tail cyclic analogues of drosocin and apidaecin, as well as their corresponding cyclic dimers. Only the large cyclic dimer of apidaecin partially retained the antimicrobial activity, suggesting that a bending of the peptide chain, in particular in the middle of the molecule, is not a structural element characteristic of the bioactive conformation of drosocin and apidaecin.
CONCLUSION: Experiments aimed at testing the effect of selected drosocin and apidaecin peptides on biological membranes showed that some peptides display a moderate hemolytic activity and that a dissociation between antibacterial activity and cytotoxicity to eukaryotic cells can be achieved in differently glycosylated peptide analogues.
2- Goobo M et al. J Med Chem (2009)
Substitution of the arginine/leucine residues in apidaecin Ib with peptoid residues: effect on antimicrobial activity, cellular uptake, and proteolytic degradation
BACKGROUND: Several aspects of the mechanism of action of Pro-rich antimicrobial peptides, together with their low toxicity in mammalian cells, make them good candidates for the development of new antibiotic agents.
OBJECTIVE: Effect induced in the insect antimicrobial apidaecin Ib
METHOD/RESULTS: We investigated the effect induced in the insect antimicrobial peptide apidaecin Ib by the replacement of a single arginine/leucine residue with a N-substituted glycine. The resulting peptoid-peptide hybrids are more resistant to proteolysis and devoid of any significant cytotoxic activity, but moving the [NArg]residue from the N- to the C-terminal end of the molecule progressively reduces the antibacterial activity. Cell uptake experiments in E. coli cells suggest that the loss of antibacterial activity of [NArg(17)]apidaecin is a consequence of its inability to translocate into bacterial cells.
CONCLUSION: Conversely, apidaecin Ib and its peptoid-peptide hybrids are able to cross the plasma membrane in eukaryotic cells and to diffuse in the cytosol, although their translocating ability is far less effective than that of other known cell permeant peptides.