Mechanism of proton/substrate coupling in the heptahelical lysosomal transporter cystinosin (Articolo in rivista)

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Label
  • Mechanism of proton/substrate coupling in the heptahelical lysosomal transporter cystinosin (Articolo in rivista) (literal)
Anno
  • 2012-01-01T00:00:00+01:00 (literal)
Alternative label
  • Ruivo R, Bellenchi GC, Chen X, Zifarelli G, Sagné C, Debacker C, Pusch M, Supplisson S, Gasnier B. (2012)
    Mechanism of proton/substrate coupling in the heptahelical lysosomal transporter cystinosin
    in Proceedings of the National Academy of Sciences of the United States of America
    (literal)
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  • Ruivo R, Bellenchi GC, Chen X, Zifarelli G, Sagné C, Debacker C, Pusch M, Supplisson S, Gasnier B. (literal)
Pagina inizio
  • E210 (literal)
Pagina fine
  • 217 (literal)
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  • 109 (literal)
Rivista
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  • PMID: 22232659 (literal)
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  • Pubblicazione (literal)
Note
  • ISI Web of Science (WOS) (literal)
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  • CNR-IGB \"ABT\" (literal)
Titolo
  • Mechanism of proton/substrate coupling in the heptahelical lysosomal transporter cystinosin (literal)
Abstract
  • Secondary active transporters use electrochemical gradients provided by primary ion pumps to translocate metabolites or drugs \"uphill\" across membranes. Here we report the ion-coupling mechanism of cystinosin, an unusual eukaryotic, proton-driven transporter distantly related to the proton pump bacteriorhodopsin. In humans, cystinosin exports the proteolysis-derived dimeric amino acid cystine from lysosomes and is impaired in cystinosis. Using voltage-dependence analysis of steady-state and transient currents elicited by cystine and neutralization-scanning mutagenesis of conserved protonatable residues, we show that cystine binding is coupled to protonation of a clinically relevant aspartate buried in the membrane. Deuterium isotope substitution experiments are consistent with an access of this aspartate from the lysosomal lumen through a deep proton channel. This aspartate lies in one of the two PQ-loop motifs shared by cystinosin with a set of eukaryotic membrane proteins of unknown function and is conserved in about half of them, thus suggesting that other PQ-loop proteins may translocate protons. (literal)
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