(Science: amino acid) One of the 20 amino acids directly coded for in proteins. Structure differs from all the others, in that its side chain is bonded to the nitrogen of the _ amino group, as well as the _ carbon. This makes the amino group a secondary amine and so proline is described as an imino acid. Has strong influence on secondary structure of proteins and is much more abundant in collagens than in other proteins, occurring especially in the sequence glycine proline hydroxyproline. A proline rich region seems to characterise the binding site of SH3 domains. An amino acid that is found in many proteins (especially collagen).One of 20 amino acids commonly found as part of a protein.