Lipidated Peptide Dendrimers Killing Multidrug-Resistant Bacteria

Abstract

New antibiotics are urgently needed to address multidrug-resistant (MDR) bacteria. Herein we report that second-generation (G2) peptide dendrimers bearing a fatty acid chain at the dendrimer core efficiently kill Gram-negative bacteria including Pseudomonas aeruginosa and Acinetobacter baumannii, two of the most problematic MDR bacteria worldwide. Our most active dendrimer TNS18 is also active against Gram-positive methicillin-resistant Staphylococcus aureus. Based on circular dichroism and molecular dynamics studies, we hypothesize that TNS18 adopts a hydrophobically collapsed conformation in water with the fatty acid chain backfolded onto the peptide dendrimer branches and that the dendrimer unfolds in contact with the membrane to expose its lipid chain and hydrophobic residues, thereby facilitating membrane disruption leading to rapid bacterial cell death. Dendrimer TNS18 shows promising in vivo activity against MDR clinical isolates of A. baumannii and Escherichia coli, suggesting that lipidated peptide dendrimers might become a new class of antibacterial agents.

Antimicrobial Peptide Dendrimer Chimera

“…Cyclic peptide 2 2 > 2000 bH1 [25] (L) 8 (BL) 4 (BF) 2 BK 22 (7) 2401.1/2400.0 16 n.d. [g] > 300 G3KL [34] (KL) 8 [34] (OF) 4 (KBL) 2 KKLK(C 10 ) 121 (42) 2395.61/2395.61 2 8 500 T7 [37] (KL) 8 Dendrimer chimera:…”

“…TNS03 [34] (KL) 4 substituting the side-chain decanoylated lysine in G0 of TNS18 with a LL dipeptide occurring in G1 of T7. We then prepared three G3 dendrimer chimera between TNS18 and G3KL using the G3KL sequence either only at G0 (DC2), at G1 and G0 (DC3), or at G2, G1, and G0 (DC4).…”

“…These results were in line with vesicle leakage data for the parent AMPDs G3KL, TNS18, and T7. [34,37] Note that activity of AMPs and AMPDs on neutral EYPC vesicles as well as their hemolysis activity generally increases with the fraction of hydrophobic residues.…”

“…To test whether the conformations observed by CD might indeed be present in dendrimer DC5, we performed molecular dynamics (MD) simulations using GROMACS [41] over 500 ns in pure water or with 20 % v/ v TFE starting from a conformer with (φ,ψ)-dihedral angles of all residues set in an α-helical conformation, as previously reported with other dendrimers. [34,37,42] Dendrimer DC5 rapidly unfolded in water to a hydrophobically collapsed conformation containing a mix of random coil and β-sheet structures, as indicated by the distribution of the Ramachandran angles, with leucines clustered towards the dendrimer center and Lys side chains pointing outwards, with a relatively compact conformation at an average radius of gyration of 1.2 nm (Figure 4a, 4b, 4d, and 4e).…”

“…TNS18 contains four ornithine-phenylala-nine (OF) dipeptides in the G2 branches and two diaminobutyryl-leucine (BL) dipeptides in the G1 branches, which are combined with extension of the G0 core with a side-chain decanoylated lysine to enhance membrane affinity. [34] TNS18 is as active as G3KL on Gram-negative strains, but in addition shows measurable activity on the Gram-positive bacterium Staphylococcus aureus including the methicillin resistant strain MRSA.…”