Fig. 1: Cryo-EM structure of ASCT2 in lipid nanodiscs in the presence of Na⁺ and glutamine.

a Impact of Na⁺ ions on glutamine transport mediated by ASCT2 measured in a radioactive uptake assay at indicated salt conditions. Data show the exchange of glutamine in the presence of internal and external Na⁺ ions (green circles); exchange of glutamine with internal K⁺ ions and external Na⁺ ions (yellow triangle); exchange of glutamine with internal Na⁺ ions and external K⁺ ions (pink square); and exchange of glutamine in the presence of internal and external K⁺ ions (blue diamond). Data points and error bars represent mean values ± SEM from n = 2 biologically independent experiments, each done in two or three technical replicates. Source data are provided as a Source Data file. b Cryo-EM map of trimeric ASCT2 in lipid nanodiscs in the presence of Na⁺ ions and glutamine in an outward-facing state with closed HP2 gate (Gln-Na⁺-OFS^HP2-cld) at 2.6 Å resolution, countered at 5σ. Each protomer is colored according to respective domains: scaffold domain in yellow, transport domain in blue, and HP2 region in salmon. The surrounding nanodisc is shown as a transparent unsharpened map at a lower countered level (3.7σ). The view is shown from the membrane side and the membrane boundaries are indicated as lines. c The cryo-EM structure of one ASCT2 protomer in the outward-occluded state (Gln-Na⁺-OFS^HP2-cld). The scaffold domain is colored in yellow and the transport domain in blue. The closed HP2 gate is displayed in salmon, while glutamine and Na⁺ ions are in light cyan and pink, respectively. The membrane boundaries are indicated as lines. d Close-up view of the substrate binding pocket highlighting the interactions between glutamine (light cyan) and the transport domain with the coordinating displayed as sticks. e–g A close-up view of the Na⁺ ions (pink) bound at Na1 (e), Na2 (f), and Na3 (g) sites with displayed coordinating residues.