Biological complexity: ion channel pores (Introduction)

by David Turell , Wednesday, March 18, 2020, 19:34 (1498 days ago) @ David Turell

A new discovery of how they work:

https://medicalxpress.com/news/2020-03-ball-and-chain-inactivation-ion-channels-visuali...

"Ion channels, which allow potassium and sodium ions to flow in and out of cells, are crucial in neuronal 'firing' in the central nervous system and for brain and heart function. These channels use a "ball-and-chain" mechanism to help regulate their ion flow, according to a new study led by Weill Cornell Medicine scientists.

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"Many types of ion channels, including those necessary for neuronal signaling and the beating of the heart, will physically open, allowing a flow of ions in or out of the cell, when a certain stimulus is applied. However, in order to switch ion flow on and off with high enough frequencies to meet the demands of neurons, heart muscle cells and other cell types, some ion channels need an additional, on-the-fly mechanism to stop ion flow—even when the stimulus is still present and the channel structure is in principle in the "open" state.

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"With low-temperature electron microscopy (cryo-EM), which bounces electrons instead of light off objects to make atomic-resolution images of them, the scientists obtained pictures of the MthK channel when it was switched open by calcium and switched closed. The pictures revealed that even when the MthK channel is in the calcium-activated, "open" state, the pathway through which ions flow was plugged by a flexible element that sticks into the pore of the channel structure.

"The scientists confirmed the function of this plug mechanism by showing that when the 'ball-and-chain' was deleted genetically, the flow of potassium ions through the calcium-activated MthK channel was no longer regulated."

Comment: this irreducibly complex mechanism cannot be developed by chance. Only design achieves this.