Identification and analysis of collagen α1(XXI), a novel member of the FACIT collagen family

The FACIT collagens bind to the surface of collagen fibrils linking them with other matrix molecules. Bioinformatics analysis of cDNA clone DKFZp564B052 showed that it resembled the FACIT collagens and was therefore designated collagen α1(XXI). Phylogenetic analyses of the N-terminal NC3 domains of α1(XXI) and other FACIT collagens showed that (i) α1(XXI) clustered with the FACIT collagens; (ii) collagen α1(XXI) arose before the divergence of α1(XII), α1(XIV) and α1(XX); (iii) collagen α1(XIV) derived from the C-terminal region of the NC3 domain of a collagen α1(XII)-like molecule; and (iv) collagen α1(XX) derived from a collagen α1(XIV)-like molecule. This study provides a framework for the evolution of the FACIT collagens which will be of value in linking NC3 domains with their functions.