3JCG

Cryo-EM structure of the magnesium channel CorA in the magnesium-free, asymmetric open state I

Summary for 3JCG

• Entry DOI: 10.2210/pdb3jcg/pdb
• Related: 3JCF 3JCH
• EMDB information: 6551 6552 6553
• Descriptor: Magnesium transport protein CorA (1 entity in total)
• Functional Keywords: membrane protein, ion channel, magnesium channel, pentameric complex, symmetry vs. asymmetry, conformational change, gating mechanism, direct electron detector, k2, transport protein
• Biological source: Thermotoga maritima
• Total number of polymer chains: 5
• Total formula weight: 207490.41

Authors

Matthies, D.,Perozo, E.,Subramaniam, S. (deposition date: 2015-12-11, release date: 2016-02-17, Last modification date: 2024-02-21)

Primary citation

Matthies, D.,Dalmas, O.,Borgnia, M.J.,Dominik, P.K.,Merk, A.,Rao, P.,Reddy, B.G.,Islam, S.,Bartesaghi, A.,Perozo, E.,Subramaniam, S.
Cryo-EM Structures of the Magnesium Channel CorA Reveal Symmetry Break upon Gating.
Cell(Cambridge,Mass.), 164:747-756, 2016

PubMed Abstract: CorA, the major Mg(2+) uptake system in prokaryotes, is gated by intracellular Mg(2+) (KD ∼ 1-2 mM). X-ray crystallographic studies of CorA show similar conformations under Mg(2+)-bound and Mg(2+)-free conditions, but EPR spectroscopic studies reveal large Mg(2+)-driven quaternary conformational changes. Here, we determined cryo-EM structures of CorA in the Mg(2+)-bound closed conformation and in two open Mg(2+)-free states at resolutions of 3.8, 7.1, and 7.1 Å, respectively. In the absence of bound Mg(2+), four of the five subunits are displaced to variable extents (∼ 10-25 Å) by hinge-like motions as large as ∼ 35° at the stalk helix. The transition between a single 5-fold symmetric closed state and an ensemble of low Mg(2+), open, asymmetric conformational states is, thus, the key structural signature of CorA gating. This mechanism is likely to apply to other structurally similar divalent ion channels.

PubMed: 26871634
DOI: 10.1016/j.cell.2015.12.055

Experimental method

ELECTRON MICROSCOPY (7.06 Å)