Transportéry

Transportéry (singular transportér) are membrane proteins that mediate the movement of substances across biological membranes. They enable the uptake of nutrients, the removal of wastes, ion balance and signaling by relocating molecules such as sugars, amino acids, ions, drugs and metabolites. Transportéry can operate passively, using existing concentration or electrochemical gradients, or actively, consuming energy to move substrates against gradients.

Two broad classes are commonly distinguished: carriers or transportéry that change conformation to move substrates (facilitated diffusion and secondary active transport) and pumps that use energy to drive transport (primary active transport). Primary active transport includes P-type ATPases, V- and F-type ATPases, and ATP-binding cassette (ABC) transporters. Secondary active transport uses the energy of ion gradients, as in solute carrier (SLC) transporters, which function as symporters or antiporters. In parallel, channel proteins provide pores that permit diffusion of ions or small molecules, but they are typically categorized separately from transportéry, though they contribute to membrane transport.

Examples include the glucose transporter GLUT1 (facilitating glucose diffusion), the sodium-glucose cotransporter SGLT1 (secondary active transport), the Na+/K+-ATPase pump (maintains ion gradients), and P-glycoprotein (ABCB1, drug efflux). The CFTR protein, an ABC transporter that functions as a chloride channel, illustrates the diversity of transporter mechanisms.

Because transporter function affects physiology, pharmacokinetics and disease, transportéry are key targets in medicine and biotechnology. Defects can cause metabolic disorders or alter drug disposition.

See also: membrane transport protein, active transport, facilitated diffusion, ABC transporters, SLC transporters, channels.