8DKI

Cryo-EM structure of cystinosin in a lumen-open state

Summary for 8DKI

• Entry DOI: 10.2210/pdb8dki/pdb
• EMDB information: 27489
• Descriptor: Isoform 2 of Cystinosin, Fab 3H5 Heavy Chain, Fab 3H5 Kappa chain (3 entities in total)
• Functional Keywords: cystine, transporter, lysosome, membrane protein, membrane protein-transport protein complex, membrane protein/transport protein
• Biological source: Homo sapiens (human); More
• Total number of polymer chains: 3
• Total formula weight: 98316.87

Authors

Schmiege, P.,Li, X. (deposition date: 2022-07-05, release date: 2022-09-21, Last modification date: 2024-10-23)

Primary citation

Guo, X.,Schmiege, P.,Assafa, T.E.,Wang, R.,Xu, Y.,Donnelly, L.,Fine, M.,Ni, X.,Jiang, J.,Millhauser, G.,Feng, L.,Li, X.
Structure and mechanism of human cystine exporter cystinosin.
Cell, 185:3739-3752.e18, 2022

PubMed Abstract: Lysosomal amino acid efflux by proton-driven transporters is essential for lysosomal homeostasis, amino acid recycling, mTOR signaling, and maintaining lysosomal pH. To unravel the mechanisms of these transporters, we focus on cystinosin, a prototypical lysosomal amino acid transporter that exports cystine to the cytosol, where its reduction to cysteine supplies this limiting amino acid for diverse fundamental processes and controlling nutrient adaptation. Cystinosin mutations cause cystinosis, a devastating lysosomal storage disease. Here, we present structures of human cystinosin in lumen-open, cytosol-open, and cystine-bound states, which uncover the cystine recognition mechanism and capture the key conformational states of the transport cycle. Our structures, along with functional studies and double electron-electron resonance spectroscopic investigations, reveal the molecular basis for the transporter's conformational transitions and protonation switch, show conformation-dependent Ragulator-Rag complex engagement, and demonstrate an unexpected activation mechanism. These findings provide molecular insights into lysosomal amino acid efflux and a potential therapeutic strategy.

PubMed: 36113465
DOI: 10.1016/j.cell.2022.08.020

Experimental method

ELECTRON MICROSCOPY (3.32 Å)