Figure 1. Structure and molecular dynamics of the outer membrane.
(1) LPS containing hexa-acylated lipid A and long O-antigen side chain is less fluid. Non-covalent cross-bridging of neighboring LPS molecules by divalent cations (e.g. Ca2+) contributes to the OM rigidity. (2) LPS containing penta-acylated lipid A and short O-antigen side chain is more fluid. (3) OMP islands formed by promiscuous interactions between OMPs display restricted mobility.[8] Old OMP islands (predominantly at cell poles) and new OMP islands (predominantly at mid-cells) are color-coded. (4) Top view of the interaction between trimeric porin (blue) and LPS (red).[39] One interaction site is stabilized by Ca2+ (yellow). (5) Gliding motility machinery in myxobacteria. Proton motive force indicated with an arrow. Helical movement of motility motors are shown. (6) TraA, TraB, OM lipoproteins and LPS are fluid in myxobacteria.