Membrane transport protein

Definition

A membrane transport protein is a special kind of transmembrane protein associated with a biological membrane that facilitates the movement of one or more of these across the membrane: ions, small molecules, or macromolecules (such as other proteins). Note that a specific membrane transport protein may facilitate the movement of only a few specific ions across the biological membrane.

Relation with other terminology

• Membrane transport proteins associated with a biological membrane are transmembrane proteins for that biological membrane. Concretely, transmembrane proteins are proteins permanently attached to both layers of the lipid bilayer that the membrane is made up of. A membrane transport protein must be a transmembrane protein since it needs to be on both sides in order to facilitate movement from one side to another.
• Transmembrane proteins are, in turn, instances of integral membrane proteins, i.e., proteins permanently attached to a biological membrane.
• Integral membrane proteins are, in turn, instances of membrane proteins, i.e., proteins that interact with a biological membrane.