Model membrane approaches to determine the role of calcium for the antimicrobial activity of friulimicin

Katrin Reder-Christ (1) , Hildegard Falkenstein-Paul (1) , Gabriela Klocek , Saad Al-Kaddah (1) , Udo Bakowsky (2) , Gerd Bendas (1)

1 Department of Pharmacy
2 Department of Pharmacy

Friulimicin is a cyclic lipopeptide antibiotic, currently in clinical development, that possesses excellent activity against Gram-positive bacteria, including multiresistant strains. A recent study on the mode of action of friulimicin reported on the interference with bacterial cell wall biosynthesis via a calcium-dependent complexing of the bactoprenol phosphate carrier C-P. The calcium dependency of this non-common targeted activity remains to be elucidated. In the present model membrane approach, the role of calcium for friulimicin targeting to C-P was investigated by biosensor-based detection of binding affinities. The findings were supplemented by atomic force microscopy (AFM) and circular dichroism (CD) spectroscopy. Comparing the calcium salt of friulimicin with the calcium-free peptide, calcium appeared to be essential for friulimicin interaction with 1,2-dioleoyl--glycero-3-phosphocholine (DOPC) model membranes. The binding affinity was even higher in the presence of 0.1 mol% C-P (0.21μM vs. 1.22μM), confirming the targeted mode of action. Binding experiments with supplemented calcium salts suggest (i) the phosphate group as the essential moiety of C-P, referring to a bridging function of calcium between the negatively charged friulimicin and C-P, and (ii) a structural effect of calcium shifting the peptide into a suitable binding conformation (CD spectra). AFM images confirmed that calcium has no, or only a minor, effect on the aggregate formation of friulimicin. These data shed new light on the mechanisms of antibacterial activity of friulimicin.

Mots clés: Cyclic lipopeptides; Atomic force microscopy; Biosensor; C55-P; Friulimicin

Domaines: Microbiologie et Parasitologie

Katrin Reder-Christ, Hildegard Falkenstein-Paul, Gabriela Klocek, Saad Al-Kaddah, Udo Bakowsky, et al.. Model membrane approaches to determine the role of calcium for the antimicrobial activity of friulimicin. International Journal of Antimicrobial Agents, 2011, 37 (3), pp.256. ⟨10.1016/j.ijantimicag.2010.11.024⟩. ⟨hal-00671247⟩