PURIFICATION OF UBIQUITIN FROM GOLDFISH (CARASSIUS-AURATUS) OOCYTE CYTOSOL

Ubiquitin was purified from the cytosol fraction (150,000 g supernatan t) of goldfish ovaries containing full-grown postvitellogenic oocytes using four steps of column chromatography. The purified goldfish ubiqu itin gave a single band with a molecular weight of 5.5 kDa on denaturi ng polyacrylamide gel electrophoresis and reacted with an anti-bovine ubiquitin antibody on Western blot. The first 40 amino acid residues o f the N-terminal sequence of goldfish ubiquitin are identical with tho se of ubiquitins in other higher eukaryotes. These results indicate th at ubiquitin exists and occurs as a free polypeptide in immature oocyt es of goldfish.