Role of the residual nucleoprotein complex and acidic proteins of the cell nucleus in protein synthesis.

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Abstract
Ribosomal ribonucleic acid(RNA), polyadenylic acid (poly A), and polyuridylic acid (poly U) did not stimulate the incorporations of C14-tryptophan nor Cl4-phenylalanine into isolated residual nucleoprotein complex from calf thymus nuclei. This and previously reported ineffectiveness of sRNA and ribonuclease (RNase) upon C14-tryptophan incorporation, suggested that the residual system differs from the ribosomal synthetic mechanism. Electron microscopy and sedimentation analysis on fractionated residual nucleoprotein complex enabled morphological description of the many molecular species of the complex. These studies revealed that the residual complex is composed of 4S, 11S, 13S, 17S, and 22S components. The slow-sedimenting components were in the form of spheres of 50-250 A in diameter; the fast-sedimenting components, strands measuring 100-300 A in width. Most of the RNA was concentrated in the spherical particles. The incorporating activity of the residual complex was related to its RNA content. Alkali-soluble acidic proteins were prepared from fractions of the residual nucleoprotein complex and were rich in RNA. The correlation between the acidic proteins and the protein synthetic activity of the residual comples was discussed.