particles present in animal cells and consisting of macromolecular (nonribosomal) ribonucleic acid (RNA) and a special protein.

Informosomes were first discovered by the Soviet biochemist A. S. Spirin and his co-workers (1964) in the cytoplasm of fish embryos, where they are represented by a mixture of particles of various sizes (molecular weights, 500,000 to 50 million and more). The ratio of the weight of the RNA to the weight of the protein in informosomes is constant (approximately 1:4) and identical in all particles, regardless of size. Analogous particles are found in the cells of mammals (including those infected with viruses), echinoderms, and insects. Informosomes apparently contain messenger RNA (m-RNA). The protein of informosomes probably serves to transfer m-RNA from nucleus to cytoplasm, to protect m-RNA from destruction, and to regulate the rate of protein synthesis.