To better understand the role of the unique domain Y153-R204, the surface of the protein was analysed in terms of its electrostatic potential. In Figure , the surface of AcmB is shown with the positively charged amino acids (arginine, lysine, and histidine) marked in blue, and the negatively charged amino acid residues (aspartic acid, glutamic acid) are coloured red. The highest concentration of positively charged amino acids is observed within the putative membrane-associated domain (marked with a black dashed line). This observation further supports the suggested role of domain Y153-T204 in the interaction with the lipid bilayer of membranes.