4OH3

Crystal structure of a nitrate transporter

Summary for 4OH3

• Entry DOI: 10.2210/pdb4oh3/pdb
• Descriptor: Nitrate transporter 1.1, DODECYL-BETA-D-MALTOSIDE, NITRATE ION (3 entities in total)
• Functional Keywords: membrane protein, major facilitator superfamily, nitrate transporter, membrane, tranport protein
• Biological source: Arabidopsis thaliana (mouse-ear cress,thale-cress)
• Cellular location: Membrane; Multi-pass membrane protein: Q05085
• Total number of polymer chains: 2
• Total formula weight: 132760.40

Authors

Sun, J.,Bankston, J.R.,Payandeh, J.,Hinds, T.R.,Zagotta, W.N.,Zheng, N. (deposition date: 2014-01-16, release date: 2014-03-05, Last modification date: 2014-03-12)

Primary citation

Sun, J.,Bankston, J.R.,Payandeh, J.,Hinds, T.R.,Zagotta, W.N.,Zheng, N.
Crystal structure of the plant dual-affinity nitrate transporter NRT1.1.
Nature, 507:73-77, 2014

PubMed Abstract: Nitrate is a primary nutrient for plant growth, but its levels in soil can fluctuate by several orders of magnitude. Previous studies have identified Arabidopsis NRT1.1 as a dual-affinity nitrate transporter that can take up nitrate over a wide range of concentrations. The mode of action of NRT1.1 is controlled by phosphorylation of a key residue, Thr 101; however, how this post-translational modification switches the transporter between two affinity states remains unclear. Here we report the crystal structure of unphosphorylated NRT1.1, which reveals an unexpected homodimer in the inward-facing conformation. In this low-affinity state, the Thr 101 phosphorylation site is embedded in a pocket immediately adjacent to the dimer interface, linking the phosphorylation status of the transporter to its oligomeric state. Using a cell-based fluorescence resonance energy transfer assay, we show that functional NRT1.1 dimerizes in the cell membrane and that the phosphomimetic mutation of Thr 101 converts the protein into a monophasic high-affinity transporter by structurally decoupling the dimer. Together with analyses of the substrate transport tunnel, our results establish a phosphorylation-controlled dimerization switch that allows NRT1.1 to uptake nitrate with two distinct affinity modes.

PubMed: 24572362
DOI: 10.1038/nature13074

Experimental method

X-RAY DIFFRACTION (3.25 Å)