Showing papers by "David Baltimore published in 1968"

Polypeptide cleavages in the formation of poliovirus proteins

Abstract: The final step in poliovirus morphogenesis appears to be the combination of viral RNA with a protein shell called the procapsid.(1) Concomitant with the union of the RNA and the procapsid there is a cleavage of one of the procapsid proteins, producing two of the four proteins of the virion. We have now found that cleavages play an important role in the formation of most if not all poliovirus-specific proteins. Although most mammalian messenger RNA's appear to be monocistronic, it seems possible that a cleavage mechanism may function in the synthesis of some mammalian cell proteins.

Isopycnic Separation of Subcellular Components from Poliovirus-Infected and Normal HeLa Cells

Abstract: A rapid method for determining the density of ribonucleoprotein particles and complexes has been developed. The method involves glutaraldehyde fixation of sucrose gradient fractions and immediate centrifugation for 5 hours through preformed cesium chloride gradients. There is little or no aggregation of particles, so that components which co-sediment in sucrose gradients are resolved by the cesium chloride gradient. By this method the densities of HeLa cell ribosomes, polyribosomes, and subribosomal particles have been determined. Furthermore, the poliovirus replication complex has been separated from polyribosomes and its density has been found to be unaffected by treatment with ethylene-diaminetetraacetic acid.