Molecular evolution of biologically active polypeptides

Abstract

Any biological function is at least bimolecular and involves primarily a specific recognition between the shapes (conformations) of the reacting molecules. The selective, pressure of evolution therefore acted on the interaction so that coordinated changes probably occurred in two lines of molecules. Because the structure of the specific partner (receptor, macromolecular substrate, naturally occurring inhibitor, antigen, etc.) is rarely known, evolutionary speculations are often arbitrarily limited to the active polypeptide. During the life of a polypeptide chain, its conformation can be modified by ligands, by ‘conformers’ or by morphogenic cleavages. Inactive preprohormones and prohormones (e. g. preproparathyrin, proopiocortin) are successively split by specific proteolytic enzymes. Several modulator - or activator-binding sites can be distinguished in addition to the active site, so that the chain can be regarded as the result of a multiple evolution.