binding_site
A biological_region of sequence that, in the molecule, interacts selectively and non-covalently with other molecules. A region on the surface of a molecule that may interact with another molecule. When applied to polypeptides: Amino acids involved in binding or interactions. It can also apply to an amino acid bond which is represented by the positions of the two flanking amino acids.
binding_or_interaction_site
http://en.wikipedia.org/wiki/Binding_site
biological_region