Fig. 4: Conformational plasticity of ASCT2 protomers in lipid nanodiscs identified under substrate-bound and substrate-free conditions.

a Structures of substrate-bound ASCT2 at three distinct conformational states: Gln-Na⁺-OFS^HP2cld (blue), Gln-Na⁺-iOFS-up^HP2cld (light pink), and Gln-Na⁺-iOFS-down^HP2cld (teal). b Structures of substrate-free ASCT2 at two distinct conformational states: Na⁺-depleted OFS^HP2op (blue) and Na⁺-depleted iOFS-up^HP2op (light pink). Each protomer is shown as a cartoon representation of the transport domain displayed in unique colors, and a surface colored in gray represents the scaffold domain. The scaffold domain acts as a reference point for the position of the transport domain in the membrane. The HP2 is displayed in salmon (closed conformation as seen in a) or purple (open conformation as seen in b).