Comparison of K Channel Families.

K channels enable potassium to flow across the membrane with great selectivity. There are four K channel families: voltage-gated K (K), calcium-activated (K), inwardly rectifying K (K), and two-pore domain potassium (K) channels. All four K channels are formed by subunits assembling into a classic tetrameric (4x1P = 4P for the K, K, and K channels) or tetramer-like (2x2P = 4P for the K channels) architecture. These subunits can either be the same (homomers) or different (heteromers), conferring great diversity to these channels. They share a highly conserved selectivity filter within the pore but show different gating mechanisms adapted for their function. K channels play essential roles in controlling neuronal excitability by shaping action potentials, influencing the resting membrane potential, and responding to diverse physicochemical stimuli, such as a voltage change (K), intracellular calcium oscillations (K), cellular mediators (K), or temperature (K).