Crystal Structure and Conformational Change Mechanism of a Bacterial Nramp-Family Divalent Metal Transporter

Aaron T Bozzi; Lukas B Bane; Wilhelm A Weihofen; Abhishek Singharoy; Eduardo R Guillen; Hidde L Ploegh; Klaus Schulten; Rachelle Gaudet

doi:10.1016/j.str.2016.09.017

Crystal Structure and Conformational Change Mechanism of a Bacterial Nramp-Family Divalent Metal Transporter

Structure. 2016 Dec 6;24(12):2102-2114. doi: 10.1016/j.str.2016.09.017. Epub 2016 Nov 10.

Authors

Aaron T Bozzi¹, Lukas B Bane¹, Wilhelm A Weihofen¹, Abhishek Singharoy², Eduardo R Guillen³, Hidde L Ploegh³, Klaus Schulten⁴, Rachelle Gaudet⁵

Affiliations

¹ Department of Molecular and Cellular Biology, Harvard University, 52 Oxford Street, Cambridge, MA 02138, USA.
² Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
³ Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, MA 02142, USA.
⁴ Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
⁵ Department of Molecular and Cellular Biology, Harvard University, 52 Oxford Street, Cambridge, MA 02138, USA. Electronic address: gaudet@mcb.harvard.edu.

Abstract

The widely conserved natural resistance-associated macrophage protein (Nramp) family of divalent metal transporters enables manganese import in bacteria and dietary iron uptake in mammals. We determined the crystal structure of the Deinococcus radiodurans Nramp homolog (DraNramp) in an inward-facing apo state, including the complete transmembrane (TM) segment 1a (absent from a previous Nramp structure). Mapping our cysteine accessibility scanning results onto this structure, we identified the metal-permeation pathway in the alternate outward-open conformation. We investigated the functional impact of two natural anemia-causing glycine-to-arginine mutations that impaired transition metal transport in both human Nramp2 and DraNramp. The TM4 G153R mutation perturbs the closing of the outward metal-permeation pathway and alters the selectivity of the conserved metal-binding site. In contrast, the TM1a G45R mutation prevents conformational change by sterically blocking the essential movement of that helix, thus locking the transporter in an inward-facing state.

Keywords: LeuT fold; MntH; Nramp; crystallography; cysteine accessibility; divalent metal transporter; microcytic anemia; natural resistance-associated macrophage protein; transition metals.

Publication types

Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Bacterial Proteins / chemistry
Bacterial Proteins / genetics
Bacterial Proteins / metabolism
Binding Sites
Cation Transport Proteins / chemistry*
Cation Transport Proteins / genetics*
Cation Transport Proteins / metabolism
Crystallography, X-Ray
Deinococcus / genetics
Deinococcus / metabolism*
Metals / metabolism*
Models, Molecular
Mutation
Protein Binding

Substances

Bacterial Proteins
Cation Transport Proteins
Metals
natural resistance-associated macrophage protein 1

Abstract

Publication types

MeSH terms

Substances

Grants and funding