A binding site is a region on a protein to which specific ligands bind. This ability of proteins to bind specific ligands forms the basis for the wide variety of functions that a protein carries out.

An equilibrium exists between unbound ligands and bound ligands. 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.

Binding sites also exhibit chemical specificity and affinity.

See also

• NTP binding site