Ribosomes that are synthesizing polypeptides in vitro on certain natural and synthetic messages are more susceptible to inactivation by colicin E3 than ribosomes treated with E3 in the absence of added message. The initiation step of protein synthesis appears to be sufficient to cause the conversion of ribosomes to a state more sensitive to colicin E3. Message and protein synthesis are not, how...

Proteomics of chloroplast ribosomes in spinach and Chlamydomonas revealed unique protein composition and structures of plastid ribosomes. These studies have suggested the presence of some ribosomal proteins unique to plastid ribosomes which may be involved in plastid-unique translation regulation. Considering the strong background of genetic analysis and molecular biology in Arabidopsis, the in...

Polysome formation in the embryos of Pinus thunbergii seeds was studied. Free ribosomes were dissociated to smaller subunits in a high salt buffer, but the complex ribosomes were not. The free ribosomes could be distinguished from monomer ribosomes derived from polysomes after RNase treatment. The monomer ribosomes present in the embryos of the dark-imbibed seeds were predominantly free ribosom...

The chemical-carcinogen-induced detachment of ribosomes from rat liver endoplasmic reticulum was studied in vitro. Incubation of postmitochondrial supernatant with 0.2 mM-diethylnitrosamine or N-2-acetylaminofluorene removed approx. 16% of membrane-bound ribosomes, measured as differences in RNA/protein values of membrane separated from unbound ribosomes by flotation. These ribosomes are also d...

Although some work has been done on the metabolism of the RNA and, to a lesser extent, of the protein in ribosomal particles (Roberts, 1960, 1961, 1962), little is known of their structure. The general physical characteristics of Escherichia coli ribosomes have been studied by Tissieres, Watson, Schlessinger & Hollingworth (1959), of yeast ribosomes by Chao & Schachman (1956), of peaseedling ri...

Ribosomes of physiologically nondividing human peripheral blood lymphocytes were studied by ultraviolet absorbance measurements of cytoplasmic extracts subjected to ultracentrifugation in sucrose gradients at high and low ionic strength. At least 70% of the total cytoplasmic ribosomes were free ribosomes which sedimented at 80 S in low salt and dissociated to 40 S and 60 S subunits in high salt...