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. Author manuscript; available in PMC: 2023 Mar 8.
Published in final edited form as: Structure. 2020 Dec 8;29(5):426–432.e8. doi: 10.1016/j.str.2020.11.014

Figure 4. Ball-and-Chain Model of SLC38A9 for mTORC1 Activation and Amino Acid Transport.

Figure 4.

At low luminal arginine, the N-plug domain dynamically samples both the inserted and released states as an equilibrium. As the concentration of luminal arginine increases, arginine molecules enter the substrate binding site of the transporter from the luminal side and the N-plug remains in the exposed state while arginine transport takes place to the cytoplasm. In the released state the N-plug could both trigger the efflux of other luminal amino acids, such as leucine, and interact with the Rag GTPases to activate the mTORC1 signaling pathways.