VITELLOGENESIS IN THE SAND WORM, NEREIS-DIVERSICOLOR

1. Vitellin (V400) was identified in mature oocytes of Nereis diversicolor as a high molecular-weight lipoglycoprotein with a relative M(r) of 400,000. The yolk protein was purified by a two-step chromatographic procedure, using gel permeation and anion-exchange chromatography. 2. Upon dissociation by SDS, vitellin was shown to release several polypeptide subunits which ranged in relative M(r) from 140,000 to 14,000. 3. Vitellogenin (Vg) was identified in the coelomic fluid as a high molecular-weight protein with a relative M(r) of 530,000. This protein is composed of a single polypeptide with a relative M(r) of 175,000 (YP175). 4. After uptake by the maturing oocyte, Vg is processed into V400 by progressive loss in molocular weight and probable cleavage. 5. Electrophoretic analysis of the oocyte protein content during oocyte growth revealed that the processing of Vg does not occur in the earlier stage of vitellogenesis. Vg accumulates in the oocytes of young females without undergoing any significant structural modification. This suggests that the activation of the vitellogenin processing in nereid oocytes depends upon the developmental stage.