Amino Acid Incorporation into Protein by Cell-free Preparations from Rat Skeletal Muscle. III. Comparisons of Activity of Muscle and Liver Ribosomes

Biochemistry ◽  
1965 ◽  
Vol 4 (2) ◽  
pp. 253-257 ◽  
Author(s):  
James R. Florini ◽  
Charles B. Breuer
Keyword(s):  
Skeletal Muscle ◽  
Amino Acid ◽  
Rat Skeletal Muscle ◽  
Amino Acid Incorporation ◽  
Acid Incorporation ◽  
Liver Ribosomes

scholarly journals The effect of ribonuclease on rat-liver ribosomes

1968 ◽  
Vol 106 (1) ◽  
pp. 263-266 ◽  
Author(s):  
R. Brentani ◽  
M. Brentani ◽  
I. Raw ◽  
J. L. M. Cunha ◽  
N. Wrotschincky
Keyword(s):  
Amino Acid ◽  
Protein Content ◽  
Rat Liver ◽  
Sedimentation Coefficient ◽  
Analytical Ultracentrifuge ◽  
Amino Acid Incorporation ◽  
Protein Ratio ◽  
Acid Incorporation ◽  
Liver Ribosomes

1. Rat-liver ribosomes lose about 50% of their amino acid-incorporating activity when preincubated with ribonuclease. 2. This preincubation results also in loss of about 50% of the original protein content and 75% of the RNA. 3. Ribosomes sedimented by ultracentrifugation, after preincubation with ribonuclease, show negligible contamination by crystalline enzyme. 4. Washing of ribosomes treated with ribonuclease releases further protein, restoring the original RNA/protein ratio. 5. The washed particle is again capable of promoting amino acid incorporation. 6. Examination of ribosomes treated with ribonuclease in the analytical ultracentrifuge reveals destruction of ribosomes, disappearance of dimers and a decrease in the sedimentation coefficient of monomers. 7. Washed ribosomes consist of even smaller particles with a sedimentation coefficient 60s.

scholarly journals The effect of whole-body X-irradiation of guinea pigs on liver ribosomes

1968 ◽  
Vol 109 (4) ◽  
pp. 495-505 ◽  
Author(s):  
E. J. Hidvégi ◽  
J. Holland ◽  
Elisabeth Bölöni ◽  
P. Lónai ◽  
F. Antoni ◽  
...  
Keyword(s):  
Amino Acid ◽  
Guinea Pigs ◽  
Sucrose Density Gradient ◽  
Whole Body ◽  
Radiation Doses ◽  
Amino Acid Incorporation ◽  
Acid Incorporation ◽  
X Irradiation ◽  
Liver Ribosomes

1. The size distribution of aggregates of liver ribosomes and their protein-synthesizing ability in vitro were studied shortly after X-irradiation of guinea pigs. 2. Sucrose-density-gradient analysis of the mitochondrial supernatant after treatment with deoxycholate revealed a gradual increase in the number of polysomes, reaching a maximum between 9 and 15 hr. after irradiation. At that period the amount of ribonucleoprotein particles reached a level 25–30% above the control. This finding was confirmed by analytical-ultracentrifugal analysis and electron microscopy. Experiments were conducted to exclude the possibility that the enrichment of polysomes in the irradiated animals had occurred during the isolation procedure. 3. The protein-synthesizing ability of total ribosomal particles was measured in vitro. This showed an increase in amino acid incorporation parallel to the progressive enrichment of polysomes. At radiation doses of up to 1000r. the protein-synthesizing capacity was dependent on the radiation dose: the higher the dose the higher the amino acid incorporation, reaching 40–60% above the control at the period of maximal polysome enrichment. Amino acid incorporation remained at this level after radiation doses of between 1000 and 3000r. The enhanced protein-synthesizing activity was due solely to the increase in the proportion of polysomes, since irradiation was without effect on the activity of single ribosomes. 4. The results of the experiments are discussed in the light of our knowledge of the effect of radiation on protein synthesis.

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