Antiporter

An antiporter (also called exchanger or counter-transporter) is a cotransporter and integral membrane protein involved in secondary active transport of two or more different molecules or ions across a phospholipid membrane such as the plasma membrane in opposite directions, one into the cell and one out of the cell. Na⁺/H⁺ antiporters have been reviewed.[1]

Comparison of transport proteins

Antiporter illustration

In secondary active transport, one species of solute moves along its electrochemical gradient, allowing a different species to move against its own electrochemical gradient. This movement is in contrast to primary active transport, in which all solutes are moved against their concentration gradients, fueled by ATP.

Transport may involve one or more of each type of solute. For example, the Na⁺/Ca²⁺ exchanger, found in the plasma membrane of many cells, moves three sodium ions in one direction, and one calcium ion in the other.