Molecular mechanism of Mg2+-dependent gating in CorA

Olivier Dalmas, Pornthep Sompornpisut, Francisco Bezanilla and Eduardo Perozo ()
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Olivier Dalmas: Institute for Biophysical Dynamics, The University of Chicago
Pornthep Sompornpisut: Faculty of Science, Chulalongkorn University
Francisco Bezanilla: Institute for Biophysical Dynamics, The University of Chicago
Eduardo Perozo: Institute for Biophysical Dynamics, The University of Chicago

Nature Communications, 2014, vol. 5, issue 1, 1-11

Abstract: Abstract CorA is the major transport system responsible for Mg2+ uptake in bacteria and can functionally substitute for its homologue Mrs2p in the yeast inner mitochondrial membrane. Although several CorA crystal structures are available, the molecular mechanism of Mg2+ uptake remains to be established. Here we use electron paramagnetic resonance spectroscopy, electrophysiology and molecular dynamic simulations to show that CorA is regulated by cytoplasmic Mg2+ acting as a ligand and elucidate the basic conformational rearrangements responsible for Mg2+-dependent gating. Mg2+ unbinding at the divalent cation sensor triggers a conformational change that leads to the inward motion of the stalk helix, which propagates to the pore-forming transmembrane helix TM1. Helical tilting and rotation in TM1 generates an iris-like motion that increases the diameter of the permeation pathway, triggering ion conduction. This work establishes the molecular basis of a Mg2+-driven negative feedback loop in CorA as the key physiological event controlling Mg2+ uptake and homeostasis in prokaryotes.

Date: 2014
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DOI: 10.1038/ncomms4590

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