Figure 1.

Representative configurations and key molecular determinants of the closed/conductive, partially open/conductive, and fully open/conductive states of KcsA. Three of four subunits of the channel are displayed as gray ribbons, SF-bound K⁺ ions are yellow spheres, and inactivating water molecules in one of the subunits are red and white spheres. Key residues are shown as sticks: T74, green; G77, orange; I100, cyan; F103, blue; T112, purple. Opening of the activation gate is shown to be slow while inactivation of the SF is fast.