Fig. 2: GltTk substrate binding site and HP2 opening.
From: Structural ensemble of a glutamate transporter homologue in lipid nanodisc environment
a Overlay of apo (cyan), holo (Asp) (cornflower blue) and Na+-only states (light blue). The shift of Met314 and Arg401 is shown with arrows. b Cryo-EM density of l-aspartate (black mesh at 5σ). c Absence of the substrate in the inward open state (density is shown as gray mesh at 5σ). d Cryo-EM density of L-TBOA (black mesh at 4σ). e Slice through of TBOA-inhibited GltTk structure (surface representation) showing an inward-oriented and outward-oriented protomer. Opening of HP2 on both sides of the membrane prevents movements of the transport domains. f Superposition (on HP1) of the transport domains in inward Na+-only, intermediate-outward holo-Asp and fully-outward TBOA-inhibited (dark blue) states. Opening of HP2 in the inward state (4.4 Å) and TBOA-inhibited state (10.4 Å) in comparison with the occluded state is measured using Cα of Val358 (shown as sphere). l-aspartate (black sticks) indicates position of the substrate-binding site.
