It, along with its 4-hydroxy version, composes some 30% of collagen.
It is highly unlikely that one would find this amino acid in either an alpha helix or beta sheet; rather it is most often found in a beta turn. A member of the alpha ketoglutarate family, it is derived from glutamate via a series of reactions including an oxidation, reduction, followed by an NADPH dependent reduction of the pyrroline double bond. It, along with its 4-hydroxy version, composes some 30% of collagen. FTP name this amino acid who has the fourth smallest molecular weight and is unique because it is the only one whose R group is bonded to the amino group.
It is highly unlikely that one would find this amino acid in either an alpha helix or beta sheet; rather it is most often found in a beta turn.
proline