water channel activity

Definition

Target type: molecularfunction

Transport systems of this type enable facilitated diffusion of water (by an energy-independent process) by passage through a transmembrane aqueous pore or channel without evidence for a carrier-mediated mechanism. [GOC:mtg_transport, ISBN:0815340729]

Water channel activity, also known as aquaporin activity, is a molecular function that describes the selective transport of water molecules across cell membranes. This process is facilitated by integral membrane proteins called aquaporins, which form channels that allow water to pass through the lipid bilayer without requiring any energy expenditure. The water channels are highly selective for water molecules, preventing the passage of ions and other solutes. The molecular mechanism of water transport through aquaporins involves the formation of a narrow pore lined with hydrophilic residues. This pore allows water molecules to pass through single file, but it is too small for ions or other solutes. The structure of aquaporins also contains a constriction zone near the center of the pore, which acts as a selectivity filter, ensuring that only water molecules can pass through. The water molecules move through the channel via a process called "single-file diffusion," where each water molecule interacts with the previous and following water molecules in the file. This mechanism allows for rapid and efficient water transport across the cell membrane, contributing to various physiological functions, including cell volume regulation, fluid balance, and nutrient transport.'
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Proteins (2)

Compounds (1)