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Protein Binding Facts

Proteins interact with other molecules by binding to them. Learn about the different types of protein binding interactions.

A protein is a series of amino acids linked together by chemical bonds. Each type of protein has a specific function. Most of the time, the function is dependent on how the protein interacts with the surrounding environment. The protein-ligand interaction is the basic form of protein binding.

Ligands and Binding Sites

A ligand is any molecule that binds to a protein. It can be an oxygen molecule or it can be another protein, such as an antibody. Ligands bind to a specific site on the protein, namely the binding site. The binding site is specific. Only one type of ligand can bind at a particular site on a protein. There may be more than one binding site on the protein.

Structural Changes in Protein

When the ligand binds to the protein, the structure of the protein changes slightly to create a secure bond. Sometimes, the binding of the ligand affects the structure of binding sites located at different regions of the protein. If this occurs, the protein may be unable to bind additional ligands, or the protein may be activated to interact with other ligands. This type of protein is known as an allosteric protein.

Substrates and Active Sites

If the ligand is changed chemically during the interaction with a protein, it is called a substrate, and the protein is known as an enzyme. The enzyme-substrate reaction occurs at the active site of the enzyme. The substrate is changed from its initial form and released from the active site of the enzyme.


Nelson, David L. Lehninger Principles of Biochemistry 4th ed. W.H. Freeman and Company. 2005

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