July 1, 2022
Transmembrane protein (TP) is a type of membrane protein that bridges the entire biological membrane to which it is permanently bound. Transmembrane proteins extend from one side of the membrane to the other. Many TPs function as gates or “loading points” that prevent or allow the transport of specific substances across biological membranes, to enter the cell, or to leave the cell in the case of by-products. In response to the shape of individual TP molecules, they may have special ways of folding or bending by which the substance passes through the biological membrane. Transmembrane proteins are polytopic proteins that aggregate and precipitate in water. Detergents or non-polar solvents are required for their extraction, although some of them (beta-barrels) can also be extracted using denaturing agents. All transmembrane proteins are integral membrane proteins (IMPs), although not all IMPs are transmembrane proteins.