Potassium ions move like Newton's balls

Potassium (K⁺) channels are essential for the correct functioning of nerves and muscles. But the mechanism by which these tiny protein pores enable the extremely fast transfer of K⁺, whilst blocking the transfer of smaller ions such as sodium remains unknown. Three papers in 1 November Nature reveal, at the molecular level, how K⁺ channels proteins work and agree on a mathematical model of K⁺ flow across the cell membrane.

João Morais-Cabral and colleagues from the laboratory of Roderick MacKinnon at Rockefeller University in New York — that gave us the first atomic-resolution picture of a K⁺ channel — shows that K⁺ ions move in a concerted fashion between two configurations, K⁺-water-K⁺-water (1,3 configuration) and water-K⁺-water-K⁺(2,4 configuration), until a third ion enters, displacing the ion on the opposite side of the queue (Nature 2001, 414:37-42).

Yufeng Zhou — also from the MacKinnon group — reports that the transport protein changes ...