Figure 3: Extracellular gates and Glu290 interactions in different functional states of LeuT.
From: A conserved leucine occupies the empty substrate site of LeuT in the Na+-free return state
For all panels a view from the extracellular side highlights the extracellular gates (orange labels) the Arg30-Asp404 salt bridge and the hydrophobic gate defined by Phe253 and Tyr108: (a) the outward-oriented, Na+-free state (molecule A, this study); (b) outward-oriented, Na+-free state (molecule B, this study) showing a different structure around Glu290; (c) Na+-bound, outward-open state2 (PDB entry code 3TT1); (d), Na+ and substrate-bound, outward-occluded state3 (PDB entry code 2A65). Glu290 is buried in the Na+-free state (a,b), which is therefore assumed to represent a neutral H+-occluded state of counter-transport.
