Evidence for a non‐helical region at the carboxyl terminus of the collagen molecule

The triple helical structure of collagen requires that glycine occupies every third position in the amino acid sequence of its constituent polypeptide chain. No deviation from this pattern has been detected so far in those regions of the chains which are known to be part of the triple helical structure. The N-terminal sequence of approximately 15 amino acids of the crland cr2chains of several vertebrate collagens, however, does not contain glycine in every third position [l-5] . Consequently, this region cannot be part of the helical structure and was, therefore, designated 'non-helical'. This conclusion was confirmed by the observation that this region is susceptible to the attack of several proteases under conditions in which the helical structure of the molecule is not disturbed.