Permease

Permeases are proteins passively transported molecules or ions through the cell membrane. You are ATP - independent. Evolutionary permeases are a heterogeneous group, that is, they were re-invented by evolution many times and can therefore be captured exhaustively only by a long list.

Cells constantly exchange materials with their environment. Normally, the cell membrane is impermeable for most substances ( especially polar substances, such as ions or larger molecules such as glucose ( = selective- permeable ) ). So that they can still be transported through the cell membrane, so-called permeases are formed.

These proteins are embedded in the cell membrane and connect the cell interior with the outside world, so that materials can be replaced. As the protein passes through the membrane, such molecules are transmembrane proteins, or " integral protein " referred to. The term permease is used only in conjunction with enzymes such as lactose permease and is there a synonym for vans.

This type of transport is referred to as secondary active transport. That is, the energy required is not derived from the hydrolysis of ATP. As an energy source is a concentration gradient of another, simultaneously transported substance. Most commonly a sodium ion or proton gradient is used for this purpose. Some permeases transporting substances passively, if they have an appropriate concentration gradient in the direction of transport. This type of transport is also a co- transport, as two different substances are transported at the same time. See proton pump.

In prokaryotes the biosynthesis of permeases is often controlled by so-called operons. I.e. that the cell produces the permeases only when they are needed. Operon by such the production of the permease is then introduced.

A known permease is the LacY and occurs in the cell membrane of bacteria. It enables the transport of lactose into the cell interior (see lac operon ).