Membrane transport | Voltage-dependent K+ channels

Voltage-dependent K + channels are the intrinsic membrane proteins that draw the cell resting potential toward K + equilibrium potential by forming a conduction pathway, or pore, through which K + selectively diffuses down the electrochemical gradient across the membrane. The voltage imposed across the cell membrane governs pore opening, hence the name voltage-dependent K + channels. These channels serve as the appropriate negative feedback to excitatory inputs on a cell when they are active by hyperpolarizing the cell membrane. In general, voltage-dependent K + channels increase their activity on membrane depolarization, this activation dampens the excitatory events that depolarize the cell membrane and/or elevate the cytosolic Ca 2+ . Voltage-dependent K + channels are widely distributed in mammalian tissues and play important physiological roles. Some of the roles that voltage-dependent K + channels play include setting the duration of action potentials and the interspike interval during repetitive firing in neurons and in the heart, secreting K + in epithelia, setting the smooth muscle tone, and determining the resonance frequency in hair cells. Voltage-dependent K + channels are made of subunits that assemble in the bilayer as tetramers to form highly selective K + channels. The tremendous diversity of voltage-dependent K + channels can be attributed to the large number of different genes present, alternative splicing, auxiliary β-subunits, and metabolic regulation.