FIGURE 2.

Overview of E. coli lactose permease embedded in a fully hydrated POPE lipid bilayer. (a) (Side view) N- and C-domains of LacY are colored brown and green, respectively. Lactose is centrally located in the binding pocket. SMD pulling is bidirectional and departs from initial sugar positions. Pulling along these two respective directions, i.e., across cytoplasmic and periplasmic half-channels, is indicated by red and blue arrows, respectively. (b) Magnification of the LacY lumen with sugar located in the binding pocket (side view as in a). Key residues participating in sugar binding along with the sugar are shown in the right panel with fragments of the LacY N- and C-domains colored blue and red, respectively (top view). The water occupying the lumen is shown in a blue surface representation. Lactose is displayed in van der Waals representation; side chains of residues Glu-269, Arg-144, and Phe-27 are shown in stick representation.