Hydrophobic Gating of Ion Permeation in Magnesium Channel CorA.

Hydrophobic Gating of Ion Permeation in Magnesium Channel CorA.

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Ion channels catalyze ionic permeation across membranes via water-filled pores.To understand how changes in intracellular magnesium concentration regulate the influx of Mg2+ into cells, we examine early events in the relaxation of Mg2+ channel CorA toward its open state using massively-repeated michael harris sunglasses molecular dynamics simulations conducted either with or without regulatory ions.The pore of CorA contains a 2-nm-long hydrophobic bottleneck which remained dehydrated in most simulations.However, rapid hydration or "wetting" events concurrent with small-amplitude fluctuations in pore diameter occurred spontaneously and reversibly.

In the absence of regulatory ions, wetting transitions are more likely and include a wet state that is significantly more stable and more hydrated.The free energy profile for Mg2+ permeation presents a barrier whose magnitude is anticorrelated to pore diameter and the extent of hydrophobic hydration.These findings support an allosteric mechanism read more whereby wetting of a hydrophobic gate couples changes in intracellular magnesium concentration to the onset of ionic conduction.