80 S ribosomes and elongation factors 1 and 2 (EF-1 and EF-2), isolated from freeze-dried porcine brain of the hypothalamic region, were used to study the interrelation between the ribosomal binding of the two factors and of phenylalanyltRNA and N-acetyl-phenylalanyl-tRNA. Complexing of ribosomes with EF-2 + /3, y-methylene-guanosine S’-triphosphate or EF-2 + GTP + fusidic acid prevented or inh...

1. The effect of spermidine on the mescaline-induced changes of brain-cortex ribosomes was studied by adding spermidine during the treatment of goat braincortex slices with mescaline. 2. Mescaline treatment of brain-cortex slices removed a portion of the endogenous spermidine from ribosomes and this removal was significantly prevented when spermidine was present during mescaline treatment. 3. S...

Emerging studies have linked the ribosome to more selective control of gene regulation. However, an outstanding question is whether ribosome heterogeneity at the level of core ribosomal proteins (RPs) exists and enables ribosomes to preferentially translate specific mRNAs genome-wide. Here, we measured the absolute abundance of RPs in translating ribosomes and profiled transcripts that are enri...

Single point mutations corresponding to the positions G2505 and G2583 have been constructed in the gene encoding E.coli 23S rRNA. These mutations were linked to the second mutation A1067 to T, known to confer resistance to thiostrepton (1). Mutant ribosomes were analyzed in vitro for their ability to direct poly(U) dependent translation, their missence error frequency and in addition their sens...

Two proteins (ribophorins I and II), which are integral components of rough microsomal membranes and appear to be related to the bound ribosomes, were shown to be exposed on the surface of rat liver rough microsomes (RM) and to be in close proximity to the bound ribosomes. Both proteins were labeled when intact RM were incubated with a lactoperoxidase iodinating system, but only ribophorin I wa...

It is generally believed that basic features of ribosomal functions are universally valid, but a systematic test still stands out for higher eukaryotic 80S ribosomes. Here we report: (i) differences in tRNA and mRNA binding capabilities of eukaryotic and bacterial ribosomes and their subunits. Eukaryotic 40S subunits bind mRNA exclusively in the presence of cognate tRNA, whereas bacterial 30S d...

Rough microsomes were incubated in an in vitro amino acid-incorporating system for labeling the nascent polypeptide chains on the membrane-bound ribosomes . Sucrose density gradient analysis showed that ribosomes did not detach from the membranes during incorporation in vitro. Trypsin and chymotrypsin treatment of microsomes at 0 ° led to the detachment of ribosomes from the membranes ; further...

Evidence is now accumulating that sub-populations of ribosomes - so-called specialized ribosomes - can favour the translation of subsets of mRNAs. Here we use a large collection of diploid yeast strains, each deficient in one or other copy of the set of ribosomal protein (RP) genes, to generate eukaryotic cells carrying distinct populations of altered 'specialized' ribosomes. We show by compara...

Four different type 1 ribosome-inactivating proteins (RIPs) with RNA N-glycosidase activity were tested for their ability to attack the large rRNA of plant ribosomes derived from tobacco plants, as well as from the plant species from which the particular RIP had been isolated. Incubation of tobacco ribosomes with RIPs isolated from either Phytolacca americana L. (pokeweed), Dianthus barbatus L....

Recent studies (l-3) from this laboratory showed that the rate and extent of amino acid incorporation into protein by rat prostatic ribosomes decreased shortly after castration. This decrease is reversed by administration of testosterone to the orchiectomized animals. It was suggested that the levels of template ribonucleic acid’ associated with prostatic ribosomes are under the control of test...