Two different interstitial collagens were isolated from the muscle layer of the marine polychaete worm Hermodice sp. (Annelida). Collagens were solubilized after limited pepsin digestion and fractionated by a differential sale precipitation procedure. Both types of interstitial collagen (Hermodice collagens A and B) appear to be homotrimers with subunit compositions (alpha A)(3) and (alpha B)(3), respectively. Both types of subunits alpha A and alpha B migrate in SDS-PAGE between the alpha 1(I) and alpha 2(I) subunits of type I collagen with an apparent molecular weight of 100,000. SLS crystallites from Hermodice collagen A exhibited a band pattern similar to that of vertebrate type I collagen, whereas collagen B showed a very different band pattern, suggesting substantial sequence differences between the two types of collagen. The amino acid composition of Hermodice collagens A and B showed marked differences
notwithstanding, both collagens fit the pattern of interstitial collagens. The A:B ratio is 1.9, as determined from the amino acid analysis. (C) 1997 Elsevier Science Inc.
