Isolation of mRNA from membrane-bound polysomes synthesizing Sepia officinalis haemocyanin in Xenopus laevis oocytes.

Isolation and translation in Xenopus laevis oocytes of the mRNAs from the nuclear pellet and the cytoplasmic supernatant of the branchial glands from Sepia officinalis, homogenized in the presence of vanadyl-ribonucleoside complexes, revealed that the membrane-bound polysomes for haemocyanin sedimented together with the nuclei. Centrifugation on a 15-50% sucrose gradient of these polysomes, released by treatment with Triton X-100, yielded a major peak of heavy ones. The messenger fraction, isolated from this heavy fraction, directed the synthesis of the large 390 000 Mr haemocyanin polypeptide chain in oocytes. A large mRNA on heavy membrane-bound polysomes thus synthesizes the whole haemocyanin chain of S. officinalis.