Dictionary of Biological Psychology
An ambiguous term used most often to describe PROTEINS that possess a BINDING SITE for a small molecule or LIGAND. Receptor is also used to describe cells specialized for sensory transduction, such as a PHOTORECEPTOR or ELECTRORECEPTOR. Receptor proteins are usually found in the cell MEMBRANE.
The binding site is typically localized on the extracellular side—the outside—of the membrane. Receptor proteins are folded so that they may traverse neuronal membranes a number of times: for example 7-transmembrane domain receptor proteins contain seven separate domains that span the entire width of the membrane. When a ligand binds to the protein, the receptor is activated resulting in a conformational change in the protein which may open a membrane channel (see ION CHANNEL) or initiate ENZYME activity in the same or an adjoining protein. An AGONIST activates receptors, an ANTAGONIST blocks them.
See also: receptor subunits; second messengers
JOHN E.DOWLING
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