A six‐armed, tenascin‐like protein extracted from the Porifera Oscarella tuberculata (Homosclerophorida)

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Abstract
A six-armed complex could be extracted from the marine sponge Oscarella tuberculata by a two-step incubation, first in Tris-buffered saline containing EDTA, then in Tris-buffered saline containing urea. The crude extracts contained, in addition, collagen fibrils with surface filaments, individual filaments resembling collagen molecules, and laminin/nidogen-like complexes. The extracts were subsequently purified by gel-filtration chromatography and low-pressure ion-exchange chromatography on DEAE-cellulose, then analyzed by SDS/PAGE and immunoblotting methods. A glycoprotein of high molecular mass was isolated, and reduced to subunits of 230 kDa. After transfer to nitrocellulose, both the complex and its subunits were faintly stained by antibodies against amphibian tenascin. Electron microscopy of the purified extracts demonstrated the presence of a large population of tenascin-like molecules and complexes of several molecules interacting with each other by their central globule.