Existence of a 400 kDa glycoprotein in the dermis of sea cucumber Apostichopus armata: partial purification and characterization

A large size (400 kDa) non-collagenous protein was detected as a major component in the extract, with neutral salt solution, from the dermis of sea cucumber Apostichopus armata. On SDS-PAGE analysis, the 400 K component shifted to a lower molecular weight component (about 200 K) by reduction with 2-mercaptoethanol, and they were both reactive for periodic acid-Schiff (PAS) reaction staining. From these results, this protein was suggested to be a glycoprotein consisting of disulfide-bonded two subunits with almost equal molecular weight (200 K). In addition to relatively high contents (>100/1,000 residues) of aspartic and glutamic acids, cysteine was also detected (6.1/1,000 residues) in amino acid analyses of this protein partially purified by anion-exchange column chromatography. These combined results suggest the structural similarity of the 400 K component to fibronectins from other vertebrate and invertebrate animals.