Comparison of collagen types of arm and mantle muscles of the common octopus (Octopus vulgaris)

Properties of muscle collagens of arm and mantle of the common octopus, Octopus vulgaris, were compared with regard to molecular species and thermal behaviour. The major collagens were isolated from pepsin-solubilized collagen preparations of these tissues by salt precipitation and were shown, by peptide mapping, to be essentially identical to each other in the triple helical domain. Alpha and beta subunits of the major collagen of the arm, in intact form (not solubilized by pepsin digestion), on electrophoresis, moved more slowly than those of the mantle. The major collagen of the arm showed higher hot-water solubility and lower thermal stability than that from the mantle muscle. These results suggested that there were some structural and functional differences between the major collagens from these tissues although they were genetically identical molecular species. In addition, immunoblot analysis revealed the existence of a minor collagen type, which corresponded to Type SQ-II collagen in decapod molluscs, in both arm and mantle muscles.