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

Published

Journal Article

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.

Full Text

Duke Authors

Cited Authors

  • Matthies, D; Dalmas, O; Borgnia, MJ; Dominik, PK; Merk, A; Rao, P; Reddy, BG; Islam, S; Bartesaghi, A; Perozo, E; Subramaniam, S

Published Date

  • February 2016

Published In

Volume / Issue

  • 164 / 4

Start / End Page

  • 747 - 756

PubMed ID

  • 26871634

Pubmed Central ID

  • 26871634

Electronic International Standard Serial Number (EISSN)

  • 1097-4172

International Standard Serial Number (ISSN)

  • 0092-8674

Digital Object Identifier (DOI)

  • 10.1016/j.cell.2015.12.055

Language

  • eng