The outer membrane proteins OmpA, FhuA, OmpF, EstA, BtuB and OmpX have unique lipopolysaccharide fingerprints

Abstract

Abstract The outer membrane of Gram-negative bacteria has a highly complex asymmetrical architecture, containing a mixture of phospholipids in the inner leaflet and in the outer leaflet they contain almost exclusively lipopolysaccharide (LPS) molecules. In E. coli, the outer membrane contains a wide range proteins with a beta barrel architecture, that vary in size from the smallest having eight strands to larger barrels composed of twenty-two strands. Here we report coarse-grain molecular dynamics simulations of six proteins from the E. coli outer membrane OmpA, OmpX, BtuB, FhuA, OmpF and EstA in a range of membrane environments, which are representative of the in vivo for different strains of E. coli. We show that each protein has a unique pattern of interaction with the surrounding membrane, which is influenced by the composition of the protein, the level of LPS in the outer leaflet and the differing mobilities of the lipids in the two leaflets of the membrane. Overall we present analyses from over 200 microseconds of simulation for each protein. Author summary We present data from over 200 microseconds of coarse-grain simulations that show the complexities of protein-lipid interactions within the outer membranes of Gram-negative bacteria. We show that the slow movement of lipolysaccharide molecules necessitate simulations of over 30 microsecond duration to achieve converged properties such as protein tilt angle. Each of the six proteins studied here shows a unique pattern of interactions with the outer membrane and thus constitute a ‘fingerprint’ or ‘signature’.

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