Receptor (biochemistry)

As receptor (from the Latin recipere, record 'or' receive ') is in biochemistry, a protein or a protein complex called, which can bind signaling molecules, which induces the signaling processes inside the cell. The receptor can either protrude from the surface of a biomembrane, to receive signals from the outside, or yourself are inside the cell. The receptor has a specific binding site for a physiological agonists.

Membrane receptors

Receptors are located on the surface of biomembranes, and are composed of proteins that are often provided with additional modifications (eg, carbohydrate chains). You have a specific fit for small molecules called ligands, or parts of larger molecules that dock after the fit -in- principle ( key-lock principle ) to the receptor structure. They are used in cell adhesion or signal transmission (e.g., from cell to cell, see also signal transduction) or the import of substances into the cell, but can also be used by viruses to invade into a host cell. Among the best known membrane receptors, the family of integrins, some of which can be physiologically activated by chemokines and thereby the ligand of the integrin can be better tied heard.

Receptors are present on both the plasma membrane as well as on the membranes of the organelles within the cell. The former are involved, to ensure contact of the cell to the outside, while the latter are essential for the functioning of the individual organelles, their contact with one another and to the cytoplasm.

After their basic mode of action of receptors are divided into ionotropic and metabotropic in the cell membrane receptors.

Intracellular nuclear receptors

Furthermore, there are ligand-binding receptors, such as steroid receptors, which are not localized in the membrane, but in the cytoplasm or nucleus of a cell. You bind for example, hydrophobic hormones such as cortisol or the Cholesterinabkömmling the hydrophilic thyroid hormone thyroxine, whereupon solve associated proteins ( heat shock proteins) from the receptor. This creates an active transcription factor that controls the expression of the genes in the nucleus.