What do you call the final protein structure formed by multiple polypeptides?

The final protein structure formed by multiple polypeptides is referred to as the quaternary structure. This level of organization occurs when two or more polypeptide chains, each with its own primary, secondary, and tertiary structure, come together to form a functional protein. The interaction between these polypeptide chains can involve various types of bonds and interactions, such as hydrogen bonds, ionic bonds, van der Waals forces, and disulfide bridges.

Understanding the quaternary structure is crucial because it is often essential for the biological function of the protein. For instance, hemoglobin, a protein responsible for oxygen transport in the blood, consists of four polypeptide subunits and exhibits quaternary structure that allows it to efficiently carry and release oxygen in response to different physiological conditions. Thus, recognizing this level of protein organization is essential for understanding how proteins achieve their diverse functions in living organisms.