1998 Volume 64 Issue 5 Pages 780-786
The major fibrillar collagen of rainbow trout skin, type I, was found to have a subunit composition of α1 (I) α2 (I) α3 (I); α3 (I) is known to be a unique subunit of bonyfish type I collagen. To investigate the primary structure of these α (I) chains, a cDNA library was prepared from mRNA of rainbow trout fibroblast and screened by use of a cDNA collagen probe. Three distinct cDNAs coding for fibrillar collagen proα chains were cloned and polypeptides encoded by these clones were denoted as RtCOL1A1, RtCOL1A2, and RtCOL1A3. Each clone encompassed 2.5 or 3.0kb and was found to code for more than the C-terminal half of proα chains. On the other hand, the α1 (I), α2 (I), and α3 (I) chains of rainbow trout skin type I collagen were isolated and characterized by sequencing of selected tryptic peptides with subsequent comparison of these sequences with the deduced amino acid sequences of rainbow trout collagen cDNAs. From these results, RtCOL1A1, RtCOL1A2, and RtCOL1A3 were identified as parts of the proα1 (I), proα2 (I), and proα3 (I) chains of rainbow trout type I collagen, respectively. When compared with human fibrillar collagens, each of RtCOLlA1 and RtCOLlA3 was found to have the highest level of amino acid sequence homology to human proα1 (I), while RICOL1A2 had the highest homology to human proα2 (I). Furthermore, RtCOL1A3 resembled RtCOL1A1 rather than RtCOL1A2; particularly, distribution of the highly conserved cysteine residues and putative crosslinking sites indicated that RtCOL1A3 was diverged from RtCOL1A1. As far as we know, this study is the first report of fish type I collagen cDNAs.
