Collagens represent a large family of extracellular matrix glycoproteins. Members of this family include the fibrillar collagens, which are involved in the formation of striated fibrils. Fibril-forming or fibrillar collagens are one of the most ancient families of extracellular matrix molecules being found throughout the metazoan kingdom from the simplest (porifera (sponges)) to the most complex animals (vertebrates). Fibrillar collagens form the major structural elements in extracellular matrices as diverse as the evolutionarily "primitive" mesoglea of cnidarians to the highly specialized connective tissues of vertebrates (e.g. bone, cartilage, skin, and tendon). Molecular features shared by all members of this family include a highly conserved C-terminal non-collagenous (NC1) domain or C-propeptide and a long collagenous domain of ~1000 amino acid residues. The NC1 domain is the most conserved part of fibrillar collagens from invertebrates to vertebrates (types I-III, V, XI, XXIV and XXVII) [1,2,3]. Fibrillar collagen NC1 domains have also been identified in choanoflagelates, which are considered the closest relatives of metazoans [4,5].

The profile we developed covers the entire fibrillar collagen NC1 domain.