Subunit composition of type I collagen from fish in Salmonoidei

It was previously shown that among fishes in the suborder Salmonoidei, chum salmon and rainbow trout which belong to Salmonidae possessed the skin Type I collagens with a subunit composition of α1α2α3, contrasted to the collagen with (α1)2α2 of ayu which belongs to Plecoglossidae. In this study, soluble skin and/or muscle Type I collagens were isolated from seven fish species in Salmonoidei and characterized with respect to their subunit composition.Chromatographic and electrophoretic analyses revealed the existence of α1α2α3 heterotrimers in the skin Type I collagens of three other salmonid fishes (Japanese char, masu salmon, and coho salmon) and their α3 chains were distinct in chromatographic behaviour on CM-cellulose from those of many other teleosts. The muscle Type I collagen of Japanese char, however, was composed virtually of an (α1)2α2 heterotrimer, although the possible presence in trace amounts of an α1α2α3 heterotrimer could not be excluded; the same result was previously obtained for the muscle Type I collagen of chum salmon. These composite results indicated the tissue-specificexpression in salmonid fish of a Type I collagen α3 gene. On the other hand, the skin or muscle Type I collagens of several non-salmonid fishes (capelin, Japanese smelt, ayu, and icefish) were found to lack an α3 chain characteristic of many groups of teleosts and existed as (α1)2α2 heterotrimers.