Two genetically distinct molecular species of octopus muscle collagen

The arm muscular tissue of an octopus, Octopus vulgaris, was subjected to limited proteolysis with pepsin and the solubilized tissue collagen was separated into two fractions by selective salt precipitation. Biochemical characterization of the major collagen fraction precipitating at 0.45 M NaCl (pH 2.6) has demonstrated that it comprises almost a single type of molecular species with structure (alpha 1)2 alpha 2, which was identified by its CNBr-peptide pattern as being similar to Type I-like collagen of octopus skin. On the other hand, the minor collagen fraction precipitating at 0.90 M NaCl (pH 2.6) was found to contain a unique gamma-chain-sized component cross-linked by disulfide bonds. Sepharose CL-4B gel filtration of the reduced gamma component revealed the presence of an alpha component, which is virtually identical in amino acid composition to the original gamma protein and bears a close resemblance to known basement membrane collagens. This unique alpha component was genetically distinct from alpha 1 and alpha 2 chains of the major muscle collagen as judged by their CNBr-peptide patterns.