Cryo-EM Structures of the Magnesium Channel CorA Reveal Symmetry Break upon Gating

Cryo-EM Structures of the Magnesium Channel CorA Reveal Symmetry Break upon Gating. Matthies, D., Dalmas, O., Borgnia, M., Dominik, P., Merk, A., Rao, P., Reddy, B., Islam, S., Bartesaghi, A., Perozo, E., & Subramaniam, S. Cell, 164(4):747-756, 2, 2016.

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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.

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 title = {Cryo-EM Structures of the Magnesium Channel CorA Reveal Symmetry Break upon Gating},
 type = {article},
 year = {2016},
 identifiers = {[object Object]},
 keywords = {asymmetry,conformational change,direct electron detector,ion channel,membrane protein structure,single-particle cryo-electron microscopy},
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 volume = {164},
 websites = {http://www.ncbi.nlm.nih.gov/pubmed/26871634},
 month = {2},
 day = {11},
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 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.},
 bibtype = {article},
 author = {Matthies, Doreen and Dalmas, Olivier and Borgnia, Mario J. and Dominik, Pawel K. and Merk, Alan and Rao, Prashant and Reddy, Bharat G. and Islam, Shahidul and Bartesaghi, Alberto and Perozo, Eduardo and Subramaniam, Sriram},
 journal = {Cell},
 number = {4}
}

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