1. Structures of intermediate transport states of ZneA, a Zn(II)/proton antiporter
- Author
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Pak, John Edward, Ekendé, Elisabeth Ngonlong, Kifle, Efrem G, O’Connell, Joseph Daniel, De Angelis, Fabien, Tessema, Meseret B, Derfoufi, Kheiro-Mouna, Robles-Colmenares, Yaneth, Robbins, Rebecca A, Goormaghtigh, Erik, Vandenbussche, Guy, and Stroud, Robert M
- Subjects
Antimicrobial Resistance ,Emerging Infectious Diseases ,Infectious Diseases ,Generic health relevance ,Antiporters ,Bacterial Proteins ,Biological Transport ,Crystallization ,Cupriavidus ,Models ,Molecular ,Protein Conformation ,Protons ,X-Ray Diffraction ,Zinc - Abstract
Efflux pumps belonging to the ubiquitous resistance-nodulation-cell division (RND) superfamily transport substrates out of cells by coupling proton conduction across the membrane to a conformationally driven pumping cycle. The heavy metal-resistant bacteria Cupriavidus metallidurans CH34 relies notably on as many as 12 heavy metal efflux pumps of the RND superfamily. Here we show that C. metallidurans CH34 ZneA is a proton driven efflux pump specific for Zn(II), and that transport of substrates through the transmembrane domain may be electrogenic. We report two X-ray crystal structures of ZneA in intermediate transport conformations, at 3.0 and 3.7 Å resolution. The trimeric ZneA structures capture protomer conformations that differ in the spatial arrangement and Zn(II) occupancies at a proximal and a distal substrate binding site. Structural comparison shows that transport of substrates through a tunnel that links the two binding sites, toward an exit portal, is mediated by the conformation of a short 14-aa loop. Taken together, the ZneA structures presented here provide mechanistic insights into the conformational changes required for substrate efflux by RND superfamily transporters.
- Published
- 2013