Our previous finding that the tumor suppressor p53 is covalently linked to 5.8S rRNA suggested functional association of p53 polypeptide with ribosomes. p53 polypeptide is expressed at low basal levels in the cytoplasm of normal growing cells in the G1 phase of the cell cycle. We report here that cytoplasmic wild-type p53 polypeptide from both rat embryo fibroblasts and MCF7 cells and the A135V...

Membrane-bound ribosomes are thought to secrete protein for export and free ribosomes to secrete protein for intracellular use. The proportion of the total ribosomes that is bound to membranes in normal mouse kidneys has been estimated by three different methods, and the results have been compared with those obtained by a fourth method used by us previously. The most valid estimates appear to b...

Membrane-bound ribosomes are thought to secrete protein for export and free ribosomes to secrete protein for intracellular use . The proportion of the total ribosomes that is bound to membranes in normal mouse kidneys has been estimated by three different methods, and the results have been compared with those obtained by a fourth method used by us previously . The most valid estimates appear to...

The effect of the inclusion of EDTA and of heparin, in media used in the isolation of mitochondria, on the mitochindrial ribosome has been investigated. 1. Mitochondria isolated from Neurospora crassa in the presence of EDTA contain only a single type of monomeric ribosome, viz. 73 S. 2. Mitochondria isolated in the presence of Mg 2÷ contain both 79-S and 73-S monomeric ribosomes. The heterogen...

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...