Cleavage of two yolk proteins from a precursor in Caenorhabditis elegans

Four yolk proteins have been identified previously in the nematode Caenorhabditis elegans. However, only two of these proteins ( yp170A and yp170B ) are found among the products of in vitro translation of nematode RNA. The other two yolk proteins ( yp115 and yp88 ) are apparently cleaved from a precursor polypeptide of approximately 180,000 Mr. This precursor has been identified as an in vitro translation product and as a metabolically unstable polypeptide in vivo. It is bound by immunoglobulin G (IgG) specific for yp115 and by IgG specific for yp88 . The immunoadsorbed material yields the same pattern of fragments on partial digestion with Staphylococcus aureus V8 protease regardless of whether anti- yp115 or anti- yp88 IgG is used in the adsorption. Like the yp170 polypeptides, the yp115 / yp88 precursor is synthesized by the intestine and secreted intact. The precursor is evidently cleaved to yield yp115 and yp88 after secretion from the intestine but independent of the presence of the gonad. Thus, cleavage probably occurs in the body cavity of the nematode.