Abstract
A ribonucleoprotein was isolated as a minor component of skeletal-muscle myofibrils and characterized. Ribonucleic acid of the high-guanine, low-uracil type constitutes about 50% of the nucleoprotein. The bulk of the protein component does not appear to be identical with the known myofibrillar proteins. In muscle homogenates about 60% of the total ribonucleic acid in the cell sediments at low speeds of centrifuging and most of this nucleic acid is associated in some way with the myofibrils.