An effector is a molecule (originally referring to small molecules but now encompassing any regulatory molecule, includes proteins) that binds to a protein and thereby alters the activity of that protein. A modulator molecule binds to a regulatory site during allosteric modulation and allosterically modulates the shape of the protein.

See also Effector cell for use of the term in immunology.

Types of effectors

• activators
• inhibitors.

Proteins