Complete primary structure of chicken collagen XIV

We have isolated and characterized several overlapping cDNA clones for chicken collagen XIV which span a total of 6.5 kpb. These clones contain an open reading frame of 5571 bp encoding the entire collagen XIV polypeptide. The predicted polypeptide has an estimated molecular mass of 205 kDa in its glycosylated form. It is composed of 1857 amino acids which are arranged in 16 individual subdomains, including a signal peptide of 28 residues. The large amino-terminal globular domain of collagen XIV (NC3) comprises 11 of these 16 subdomains. Two of them are related to the A modules of von Willebrand factor, eight show some relationship to the type III-repeats of fibronectin and one is similar to the NC4 domain of collagen IX. The carboxy-terminal triple-helical domain is composed of two collagenous segments (COL1 and COL2), which make up less than 14% of the entire molecular mass, and of two short non-collagenous domains (NC1 and NC2). A detailed analysis of our cDNA clones indicates that collagen XIV exists in two alternatively spliced forms which differ by 31 amino acids in their NC1 domain. The variant form of the polypeptide contains 1888 amino acids with a total molecular mass of 208 kDa. Our results demonstrate that collagen XIV displays a complex multidomain structure resembling that proposed for collagen XII.