What is proline residue?

Proline is a non-polar amino acid that is classified as an imino acid because its side chain is connected to the nitrogen atom of its imino group. It is unique among amino acids due to its cyclic and rigid structure which limits its conformational flexibility. The proline residue plays a crucial role in the stability and function of many proteins, especially in regions where structural rigidity is required, such as beta bends and turns. It is also important in the formation of collagen, the most abundant protein in the human body. The proline residue is commonly found in the active sites of enzymes, where it serves as a hinge or pivot point for the movement of other amino acid residues during catalysis. In addition, proline is known to play a role in protein-protein interactions and signal transduction pathways.