The Aspartate Transport Process (IMAGE) University of Groningen Caption Scheme of the transport cycle of glutamate transporters. Four states enclosed in dashed blocks represent structures observed in this work. GltTk in both apo and holo (Asp) states prefers intermediate outward conformations (apo and holo, respectively) from where it can visit both inward and fully outward conformations. Saturation with Na+ ions leads to an increase of inward open state population. Non-equilibrium conditions in vivo (membrane voltage, substrate and Na+ gradients) will lead to different steady-state distributions over the conformational ensemble. The transport domains of the individual protomers are present in four different conformations: inward open (steel blue), intermediate-outward occluded apo (cyan), intermediate-outward occluded Asp (cornflower blue), outward-open TBOA (dark blue). Scaffold domain is shown in grey. Credit Arkhipova et al, University of Groningen Usage Restrictions With credit License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.