Ruled surface underlying KcsA potassium channels.

Recent experiments have revealed that the opening and closing of the channel is controlled by concertedly rotating and tilting the ends of the alpha-helices in the KcsA ion channels. We recognize these transmembrane alpha-helices as the generating lines of the ruled surface: the hyperboloid of one sheet. The twist-to-shrink feature of the hyperboloid is adopted by KcsA channels in gating the pore as observed in experiments. Our model may shed light on understanding nature's design principles of ion channels. And the conclusions drawn from this study have implications for the design of artificial channels.