A female specific protein (FSP) was identified and purified from the ovary of the Japanese scallop Patinopecten yessoensis by immunological techniques and a combination of precipitation with distilled water, ammonium sulfate fractionation, hydroxylapatite chromatography, and gel filtration. The molecular mass was determined to be approximately 450 kDa. Three other female specific proteins, two with the same molecular mass and the other with 700 kDa, showed different electrophoretic mobility from each other on native polyacrylamide gel electrophoresis, and reacted to antiserum against purified FSP (anti-FSP) by immunoblotting. No FSP was immunologically detected in the extract of the digestive diverticula or in the concentrated hemolymph. However, the extracts from the ovary of Chlarnys farreri nipponensis and Mytilus edulis, though not those of Crassostrea gigas, reacted to anti-FSP. The amount of FSP in the ovarian extract from the scallop increased with the progressive growth of the oocytes and this protein wsa localized in the cytoplasm of the oocyte. It is assumed that the purified FSP is formed as a yolk protein in the ovary and the yolk protein is possibly composed of four molecules synthesized from the same source as this purified FSP, the antigenicity of which is partially maintained among bivalve species.
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