Thanatin Targets the Inter-Membrane Protein Complex Required for Lipopolysaccharide Transport in Escherichia coli

With the increasing resistance of many Gram-negative bacteria to existing classes of antibiotics, identifying new paradigms in antimicrobial discovery is an important research priority. Of special interest here are the proteins required for the biogenesis of the symmetric Gram-negative bacterial outer membrane. Seven Lpt proteins (LptA-G) associate in most Gram-negative bacteria to form a macromolecular complex spanning the entire envelope, which transports LPS molecules from their site of assembly at the inner membrane to the cell surface, powered by ATP hydrolysis in the cytoplasm. The periplasmic protein LptA comprises the protein bridge across the periplasm, which connects LptB2FGC at the inner membrane to LptD/E anchored in the outer membrane. We show here that the naturally occurring insect derived antimicrobial peptide thanatin targets LptA and LptD in the network of periplasmic protein-protein interactions required to assemble the Lpt complex, leading to inhibition ofLPS transport and OM biogenesis in Escherichia coli.