Cellular components of Bacillus megaterium and their role in protein biosynthesis

Abstract

The membrane complex obtained by lysing protoplasts of Bacillus megaterium in buffers of physiological strength is disrupted by exposure to buffers of low ionic strength. Under these conditions, the following fractions are obtained and separated cleanly from each other: (1) a mucoprotein fraction; (2) a phospholipoprotein fraction, seen in the electron microscope as very small spherical vesicles free from ribosomes; (3) ribonucleoprotein particles (ribosomes of 30s and 45s); (4) ribonucleic acid of low molecular weight, together with solubilized protein that included all the amino acid-activation enzymes of the cell. When the whole membrane complex or protoplasts are incubated with labelled amino acids, labelled protein appears first in the ribosomal and phospholipoprotein fractions. The greater part of this labelled protein is found in the phospholipoprotein fraction, and there is no evidence that this is derived from the ribosomes.