The structure of fibril-forming collagens.

Although collagen molecules are designed primarily to serve as constituents of supporting aggregates in various tissues, they are present as a relatively large family of proteins that exhibit a wide diversity in structural and chemical features. Molecular diversity is, of course, specified primarily by the different genes for synthesis of the various collagen chains. However, intracellular post-translational modifications of the nascent chains as well as extracellular processing of newly assembled molecules contribute to, and considerably amplify, the diversity specified by the genome. Moreover, the nature of the aggregates derived from various molecular species of collagen reflects this diversity. In this fashion, a great deal of chemical and biological variation is created in otherwise highly similar molecules such as those classified here as belonging to group 1. It is anticipated that further developments regarding these and other molecular species of collagen will considerably refine our understanding of the spectrum of structure and function associated with this unique family of proteins.