BIOCHEMICAL AND IMMUNOLOGICAL RELATIONSHIPS AMONG FIBRONECTIN-LIKE PROTEINS FROM DIFFERENT SEA-URCHIN SPECIES

Fibronectin-like proteins were purified from ovaries of the sea urchin species, Paracentrotus lividus (Pl), Sphaerechinus granularis (Sg), A rbacin lixula (Al), Pseudocentrotus depressus (Pd), and Anthocidaris c rassispina (Ac), by gelatin-Sepharose affinity chromatography. The maj or component had a molecular mass of 180 kDa and was eluted by 1 M NaC l or 8 M urea, depending on the species used. By substrate adhesion as say, we tested the biological activity of the 180 kDa protein purified from Paracentrotus lividus (P1-180K) and showed that it promotes the adhesion of homologous embryonic cells to the substrate. An antiserum, developed against Temnopleurus hardwickii fibronectin-like protein (T h-180K), was used in Western blots of the proteins purified from the f ive species. The antibody cross-reacted with Pl-180K, Pd-180K and Ac-1 80K. A peptide map of P1-180K, obtained by V8 protease partial digesti on, was compared with those obtained from the other four proteins and showed an homology between 40 and 56%. This report confirms that fibro nectin-like proteins can be purified from sea urchins on the basis of their binding to gelatin-Sepharose; the proteins differ for their bind ing affinity to gelatin and share different epitopes, suggest ing that they are members of a sea urchin fibronectin super family.