Fig. 4. Outward occluded states of Glt_Ph and LeuT.

A) Core domain of Glt_Ph (left). Substrate is occluded from extracellular and intracellular solutions by a proposed external gate (HP2) and internal gate (HP1). Right, model of the core domain gates indicating the “thin” and “thick” nature of gates. B) Core domain, TMs 3,10, and EL4 in LeuT (left). Residues proposed to make up the external gate, along with EL4, are indicated. L-leucine is occluded from both sides of the membrane. Right, model depicting the “thin” and “thick” nature of gates in LeuT. In (A) and (B) coloring scheme as in Fig. 3.