In biochemistry, a binding site is a region on a protein, DNA, or RNA to which specific other molecules and ions—in this context collectively called ligands—form a chemical bond.
Binding sites also exist on antibodies as specifically coded regions that bind antigens based upon their structure.[1]
The term saturation refers to the fraction of total binding sites that are occupied at any given time. When more than one type of ligand can bind to a binding site, competition ensues.
An equilibrium exists between unbound ligands and bound ligands.
Binding sites also exhibit chemical specificity, a measure of the types of ligands that will bond, and affinity, which is a measure of the strength of the chemical bond.
Binding sites are often an important component of the functional characterization of biomolecules. For example, the characterization the binding site of a substrate to an enzyme is essential to model the reaction mechanism responsible for the chemical change from substrate to product.
A more specific type of binding site is the transcription factor binding site, present on DNA.
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