Type XIV collagen is a varient of undulin

Abstract

We have isolated undulin, an extracellar matrix protein associated with the surface of collagen fibrils, from chicken embryos. The protein showed a molecularmolecular mass of about 600 kDa and is composed of three 210‐kDa subunits linked by reducible as well as non‐redulic bonds. In contrast to human undulin which reportedly is devoid of collagenous sequences, the chicken protein contained a short triple‐helical segment that was sensitive to digestion by bacterial collagenase. Screening of an expression library with affinity‐purified antibodies yieded two cDNA clones specific for chicken undulin. Analysis of the amino acid sequence deduced from the nucleotide sequence of these clones terminus both polypeptides contained several similar repeats related to the III modules found in fibronectin. Towards the carboxyl terminus, however the two sequences diverged substantially from each other. While the human sequence termineted in a proline‐rich segment, the chicken sequence continued with a domain related to von Willebrand factor, with a domain similar to the noncollagenous domain NC4 fo type IX collagen and with a typical collagenous triple helix, A short segment of this sequence was found to be identical with the published sequence of a bovine peptide derived from type XIV collagen. Our protein must therefore represent chicken type XIV collagen. One way to explain these results is the possibility that undulin exists in at least two alternatively spliced variants, one lacking the collagenous domain, as described initially for human undulin, and one containing the triple‐helical domain, as found in type XIV collagen. Copyright © 1992, Wiley Blackwell. All rights reserved