Critical residues of the antibiotic peptide LysMthat inhibits lipid II flipping

Small single-strand DNA/RNA phages that infect gram-negative bacteria encode lysis proteins that induce cell lysis without directly degrading the cell wall. One such protein, the 37-residue Lys M protein derived from a lysis gene of Levivirus phage M ( lys M ), completely blocks the lipid II transport activity mediated by Escherichia coli MurJ, which is essential for peptidoglycan biosynthesis. Lys M was proposed to be a single α-helical transmembrane protein that binds to MurJ and prevents its conformational transition during lipid II transport. Although Lys M possibly interacts with MurJ, the inhibition mechanism remains unclear. Here, we identified the crucial residues for Lys M function via comprehensive alanine-scanning mutagenesis. These residues were located on two surfaces in an α-helix model, probably providing surfaces interacting with MurJ in the membrane. This study provides fundamental information regarding the mechanism of Lys M inhibition.