Proteins interact with each other, work together, and perform individual steps in chain reactions, sometimes collaboratively. Affecting protein production and/or interactions can have profound effects on cellular activity.
As macromolecules, proteins can be influenced at multiple interaction sites. A protein’s active (enzymatic) site is a small fraction of its surface. This means that most of a protein’s surface is available for binding to other proteins, and for changing the shape or activity of a protein. Binding at a place other than an active site is allostery.