Gerber and Altman have suggested1 that the mechanism involved in the synthesis of fibrous proteins is different from the mechanism involved in the synthesis of globular proteins. In particular, they suggested that collagen is synthesized by the addition of polypeptides containing 70-140 amino-acids to pre-existing collagen fibres. Although the communication raised a number of interesting questions, it should be noted that the conclusions which were reached are not entirely consistent with several recent reports. They stated that the mechanism underlying the biosynthesis of fibrous proteins must be unique, since experiments on the isotopic labelling of collagen and silk fibroin indicated that specific amino-acids are labelled to varying degrees in different parts of these molecules. It is now apparent, however, that a similar situation exists in the synthesis of a number of proteins and polypeptides, including ovalbumin, ribonuclease and insulin2. Recently, Dintzis3 demonstrated non-uniform labelling of specific amino-acids in the synthesis of the globular protein hmoglobin. 1962 Nature Publishing Group.
