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Elife. 2019 Feb 4;8. pii: e41124. doi: 10.7554/eLife.41124. [Epub ahead of print]

Structures in multiple conformations reveal distinct transition metal and proton pathways in an Nramp transporter.

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Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States.


Nramp family transporters-expressed in organisms from bacteria to humans-enable uptake of essential divalent transition metals via an alternating-access mechanism that also involves proton transport. We present high-resolution structures of Deinococcus radiodurans (Dra)Nramp in multiple conformations to provide a thorough description of the Nramp transport cycle by identifying the key intramolecular rearrangements and changes to the metal coordination sphere. Strikingly, while metal transport requires cycling from outward- to inward-open states, efficient proton transport still occurs in outward-locked (but not inward-locked) DraNramp. We propose a model in which metal and proton enter the transporter via the same external pathway to the binding site, but follow separate routes to the cytoplasm, which could facilitate the co-transport of two cationic species. Our results illustrate the flexibility of the LeuT fold to support a broad range of substrate transport and conformational change mechanisms.


E. coli; biochemistry; chemical biology; molecular biophysics; structural biology

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Conflict of interest statement

AB, CZ, JN, BL, CZ, RG The authors declare that no competing interests exist.

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