Yolk granules are the major compartment for bullfrog (Rana catesbeiana) oocyte‐specific ribonuclease

• DOI: 10.1111/j.1432-1033.1994.tb18859.x
• Publication Date: 2005-03-04T07:32:34Z
• Authors: You‐Di LIAO; Jaang‐Jiun WANG
• Keywords: 0301 basic medicine; 03 medical and health sciences; Rana catesbeiana; Ribonucleases; Oocytes; Animals; Electrophoresis, Polyacrylamide Gel; Female; Tissue Distribution; Egg Yolk; Precipitin Tests; Cell Compartmentation

Rana catesbeiana ribonuclease (RC‐RNase) is a pyrimidine guanine sequence‐specific ribonuclease found only in R. catesbeiana (bullfrog) oocytes, not in other organs. An immunohistochemical assay showed that RC‐RNase was present in the regular yolk granules, but not in forming yolk granules, yolk platelets, pigment granules, mitochondria clouds or the nucleus. The RC‐RNase was restricted to the lateral amorphous area of the yolk granules, and was absent from the central area that has a vitellogenin crystal lattice. The RC‐RNase was extracted from yolk granules by 0.5 M NaCl and purified by dialysis and affinity chromatography. Most of the RC‐RNase (94%) was found in the yolk granules, the rest RC‐RNase (6%) was found in the cytosol in the form of free RNase and latent RNase. The RC‐RNase extracted from yolk granules was further analyzed by immunoprecipitation and RNase activity assay on an SDS/polyacrylamide gel. Our results suggest that the RC‐RNase activity is regulated by both compartmentation and inhibitor binding.