Figure 4: Comparison of the pathways and Glu290 accessibility in available LeuT and MhsT structures.
From: A conserved leucine occupies the empty substrate site of LeuT in the Na+-free return state
LeuT outward-facing substrate-occluded state3 (PDB entry code 2A65); MhsT inward-facing substrate-occluded state9 (PDB entry code 4US3); LeuT inward-open apo state2 (PDB entry code 3TT3); LeuT Na+ free, outward-oriented return state; and LeuT outward-open Na+-bound state2 (PDB entry code 3TT1). The Glu290 residue (or for MhsT the proposed H+-binding residue Asp263) is buried in all of the states except outward-open, where it has a direct interaction with the extracellular environment. TM1 helix and Leu25 (Leu29MhsT) are shown in pink, the Na+ ions are shown as green spheres, Glu290 (or Asp263MhsT) as cyan and substrate at the binding site as yellow spheres.
