Incorporation of radiolabelled amino acids by adult Schistosoma japonicum: further characterization of a putative eggshell precursor protein.

The synthesis patterns of female-specific proteins of Schistosoma japonicum were further investigated with particular reference to the 34 kDa putative eggshell precursor protein. Adult male and female worms of S. japonicum were metabolically labelled with 14C-tyrosine, 14C-glycine and 35S-methionine in vitro. The rates of amino acid incorporation for female worms were significantly higher than for males in all radiolabelling experiments. Labelled proteins were resolved by two-dimensional gel electrophoresis and visualized by fluorography. By using 14C-tyrosine and 14C-glycine, the 34 kDa female protein band resolved into three major spots with pI 6.0, 5.8 and 5.6. On the other hand, labelling studies using 35S-methionine failed to reveal synthesis of any corresponding spots at Mr 34 kDa. These results, together with the observations that eggshell hydrolysates are very rich in glycine but poor in methionine, suggested that the 34 kDa putative eggshell precursor protein of S. japonicum consists of at least three isoelectric forms. In addition, we have demonstrated several other female-specific polypeptides synthesized by this worm.