A transmembrane protein that facilitates the movement of specific ions or molecules across a biological membrane. These structures form a pore, allowing substances to bypass the hydrophobic core of the lipid bilayer. For example, aquaporins permit the rapid transport of water molecules into and out of cells, while specific ion channels enable the flow of sodium, potassium, or calcium ions, essential for nerve impulse transmission and muscle contraction.
These selective pathways are critical for maintaining cellular homeostasis, regulating membrane potential, and enabling cell-to-cell communication. The discovery and characterization of these proteins has significantly advanced understanding of cellular physiology and has provided targets for numerous pharmaceuticals. Historically, their existence was postulated based on observed transport phenomena before direct structural identification became possible with advancements in protein biochemistry and structural biology.
