Membrane protein

A membrane protein is an intercalated into the lipid layer of a biomembrane ( integral ) or this been superimposed (peripheral ) protein. It does not matter whether the protein intracellular organelles located in the outer membrane (plasma membrane) or in membranes. About 25 to 30 percent of all naturally occurring proteins are embedded in cell membranes.

Properties

Among the integral membrane proteins include the transmembrane proteins to the peripheral membrane proteins include membrane-bound proteins. The difference lies in whether they are run through the cell membrane completely or only one side of the lipid bilayer attached or anchored therein. Cellular proteins with portions on the cell surface will be referred to as surface proteins. Viral proteins on the surface of a virion is also referred to as surface proteins and there often bind antibodies include, but are also at the same time only in enveloped virus membrane proteins with the characteristic hydrophobic amino acid sequences. Proteins and carbohydrates on the cell surface can be used as antigens to trigger a humoral immune response and will be referred to with respect to the immune system as surface antigens.

The structure of the proteins depends on the condition. An anchored in the membrane protein often has phosphorylation, glycosylation and myristoylation, which posttranslationally influence the tertiary structure.

Membrane proteins are of great medical importance: about half of all currently approved drug acts on these type of protein as a therapeutic target.

Membrane proteins are key functional proteins since they are the one important part of the structural division of organelles; continue to play a vital role in almost all cellular functions. Mention may be made here with others:

Membrane proteins usually perform important physiological roles, eg as cell adhesion molecules, or receptors translocases of signaling pathways. Examples are porins (eg aquaporins, important for the water and energy budget) and ABC transporters as well as light receptors such as bacteriorhodopsin.

The transmembrane proteins are distinguished functionally. Transporters and channels are essential in order to ensure A. and the ion balance of a cell, enzymes catalyze important metabolic processes, receptors serve a routing of signals through a lipid layer of time, connexins establish direct connections between cells, etc.