Structural basis for proton coupled cystine transport by cystinosin

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Amino acid transporters regulate cellular nutrient flow and metabolism.
• Mutations in cystinosin cause cystinosis, a lysosomal storage disorder characterized by cystine crystal accumulation.
• Cystinosin, a PQ-loop solute carrier (SLC) transporter, exports cystine using a proton gradient, but its transport mechanism is poorly understood.

Purpose of the Study:

• To determine the molecular basis of cystinosin function and proton-coupled transport.
• To provide a structural framework for understanding cystinosis and developing new treatments.
• To investigate the mechanism of cystine recognition and transport by cystinosin.

Main Methods:

• X-ray crystallography was used to obtain structures of Arabidopsis thaliana cystinosin in apo and cystine-bound states.
• In vitro and in vivo assays were employed to characterize cystinosin function.
• Mutational mapping and functional characterization of human cystinosin were performed.

Main Results:

• Crystal structures revealed the structural basis for cystinosin function.
• A mechanism for proton-coupled cystine transport was established.
• Disease-causing mutations in human cystinosin were functionally characterized, providing insights into their molecular impact.

Conclusions:

• The study elucidates the structure-function relationship of cystinosin.
• A detailed mechanism for proton-driven cystine transport is proposed.
• This work offers a foundation for understanding cystinosis pathogenesis and therapeutic development.