Ribosomes of Trypanosoma brucei, a parasitic, flagellated protozoan (order Kinetoplastida), were identified on sucrose density gradients by their radioactively labeled nascent peptides. Ultraviolet absorption revealed only cytoplasmic ribosomes which served as internal sedimentation markers. Synthesis on cytoplasmic ribosomes was completely inhibited by cycloheximide. In the presence of this an...

1. Ribosomes isolated from the cortex tissue of goat brain contain very small amounts of spermidine and spermine. Ribosomes isolated from spermidinetreated slices have a higher spermidine content. 2. The polyamines partially prevent the temperature-dependent breakdown of ribosomes into acid-soluble nucleotides. 3. The 'melting' temperature of ribosomes rises slightly when the ribosomes are heat...

A method for the preparation of mitochondrial ribosomes from yeast is presented. Mitochondrial ribosomes differ from their cytoplasmic counterpart in nucleotide composition, electrophoretic mobility of a number of their respective ribosomal proteins, and thermal denaturation profiles. The mitochondrial and cytoplasmic ribosomes have identical sedimentation coefficients (80 S) and dissociate int...

Ribosome recycling factor (RRF), elongation factor G (EF-G) and GTP split 70S ribosomes into subunits. Here, we demonstrated that the splitting was transient and the exhaustion of GTP resulted in re-association of the split subunits into 70S ribosomes unless IF3 (initiation factor 3) was present. However, the splitting was observed with sucrose density gradient centrifugation (SDGC) without IF3...

The biosynthesis of proteins of chloroplastic (67 S) and cytoplasmic (83 S) ribosomes of Chlamydomonas reinhardi was studied in viva using both wild type and the arginine auxotroph, arg-1. The incorporation of amino acids into nascent protein (chaseable label) and ribosomal structural protein (nonchaseable label) was examined. When cells of tug-1 were incubated with excess radioactive arginine,...

Streptomycin-sensitive 70s ribosomes which are dissociated into SOS and 30s particles by dialysis against 1 X lop4 M magnesium acetate, and then reassociated in 0.02 M magnesium acetate, differ from nondissociated 70s ribosomes in r4C-aminoacyl soluble ribonucleic acid (sRNA) binding. 1. Reassociated ribosomes bind about twice as much 14C!phenylalanyl-sRNA in the presence of polyuridylic acid a...

A mixture of cytoplasmic (80S) and chloroplast (70S) ribosomes from Chlamydomonas reinhardtii was freed of contaminating membranes by sedimentation of the postmitochondrial supernatant through a layer of 1.87 M sucrose. The purified ribosomes were separated into 80S and 70S fractions by centrifugation at a relatively low speed on a 10-40% sucrose gradient containing 25 mM KCl and 5 mM MgCl(2). ...

A class of 80 S ribosomes has been isolated from purified yeast mitochondria. These ribosomes are distinguished from cytoplasmic ribosomes of the postmitochondrial supernatant fraction by having a greater stability against the dissociating effect of 0.4 M KCI. These results confirm observations of Schmitt ((1969) Fed. Eur. Biochem. Sot. Left. 4, 234-238). Ribosome dissociability has been examin...

We have developed a novel chromatography for the rapid isolation of active ribosomes from bacteria without the use of harsh conditions or lengthy procedures that damage ribosomes. Ribosomes interact with an alkyl linker attached to the resin, apparently through their RNA component. Examples are given with ribosomes from Escherichia coli, Deinococcus radiodurans, and with clinical isolates of St...

An average of 17% of rabbit reticulocyte ribosomes are closely bound to the cell membrane. Evidence is presented to indicate that membrane binding of reticulocyte ribosomes is not an artifact. Membrane-bound reticulocyte ribosomes differ in physical and chemical properties from free reticulocyte ribosomes in having a high coefficient of sedimentation (greater than 400 S) and a high protein to R...