PMID: 30714568

Authors:

Bozzi AT, Zimanyi CM, Nicoludis JM, Lee BK, Zhang CH, Gaudet R

Title:

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

Journal:

Elife. 2019 Feb 4;8. pii: 41124. doi: 10.7554/eLife.41124.

Abstract:

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.