Binding of Ribosomes to Cytoplasmic Reticulum of Bacillus megaterium

Abstract

Schlessinger, David (Washington University School of Medicine, St. Louis, Mo.), Vincent T. Marchesi, and Benjamin C. K. Kwan . Binding of ribosomes to cytoplasmic reticulum of Bacillus megaterium . J. Bacteriol. 90: 456–466. 1965.—As many as 60% of the cellular ribosomes are bound to membrane “ghosts” in lysozyme lysates in 0.02 m Mg 2+ . Bound ribosomes labeled with C 14 -uracil do not exchange with added unlabeled ribosomes, even after disruption of the cell membrane by sonic treatment. Electron micrographs of thin sections of ghosts, or of fragments produced by sonic disruption of protoplasts, indicate that the ribosomes are distributed on a reticular matrix which extends throughout the cytoplasm. The binding of ribosomes to this matrix is insensitive to ribonuclease or deoxyribonuclease, and has many other features in common with the binding of ribonucleoprotein to the membranous elements of the mammalian microsomal fraction, though the reticulum does not appear to be membranous. Thus, functioning ribosomes may be bound to a cytoplasmic structure in all cell types.