scholarly journals Inhibition by ricin of protein synthesis in vitro: 60S ribosomal subunit as the target of the toxin (Short Communication)

1973 ◽  
Vol 136 (3) ◽  
pp. 813-815 ◽  
Author(s):  
Simonetta Sperti ◽  
Lucio Montanaro ◽  
Alessandro Mattioli ◽  
Fiorenzo Stirpe
Keyword(s):  
Protein Synthesis ◽  
Rat Liver ◽  
Short Communication ◽  
Ribosomal Subunit ◽  
Site Of Action ◽  
Liver Ribosomes

Poly(U)-directed polyphenylalanine synthesis by rat liver ribosomes is strongly inhibited by ricin. Experiments involving hybridization between subunits derived from normal and ricin-treated ribosomes demonstrate that the 60S subunit is the site of action of the toxin. The toxin inactivates the 60S subunit independently of the presence of the 40S subunit.

scholarly journals Inhibition of protein synthesis in vitro by crotins and ricin. Effect on the steps of peptide chain elongation

1976 ◽  
Vol 156 (1) ◽  
pp. 7-13 ◽  
Author(s):  
S Sperti ◽  
L Montanaro ◽  
A Mattioli ◽  
G Testoni ◽  
F Stirpe
Keyword(s):  
Protein Synthesis ◽  
Rat Liver ◽  
Elongation Factor ◽  
Artemia Salina ◽  
Chain Elongation ◽  
Gtp Hydrolysis ◽  
Elongation Factor 2 ◽  
The Individual ◽  
Liver Ribosomes

The effects of crotin I and crotin II on the partial reactions of polypeptide chain elongation were investigated and compared with the known effects of ricin. Crotin II was a more powerful inhibitor than crotin I, but no qualitative differences between the two crotins were found. Rat liver ribosomes, preincubated with crotins and washed through sucrose gradients, remained inactive in protein synthesis. Among the individual steps of elongation, the peptidyltransferase reaction was unaffected by crotins, but some of the reactions that involve the interaction of elongation factors 1 and 2 with ribosomes were modified. A strong inhibition of the binding of elongation factor 2 to ribosomes and a stimulation of the elongation factor2-dependent GTP hydrolysis were observed; this indicates the formation of a very unstable elongation factor 2-GDP-ribosome complex, which, however, allows a single round of translocation to take place in the presence ofelongation factor 2 and added GTP. The elongation factor 1-dependent GTP hydrolysis was inhibited by crotins, whereas the enzymic binding of aminoacyl-tRNA, to both rat liver and Artemia salina ribosomes, was scarcely affected. In a protein-synthesizing system the inhibition by crotins and by ricin leads to a block of the nascent peptides on the ribosomal aminoacyl-tRNA site, an effect consistent with inhibition at the level of translocation. The mechanism of action of crotins appears to be very similar to that of ricin.

Protein synthesis by free and bound rat liver ribosomes in vivo and in vitro

1963 ◽  
Vol 7 (2) ◽  
pp. 122-129 ◽  
Author(s):  
Edgar C. Henshaw ◽  
Tadeusz B. Bojarski ◽  
Howard H. Hiatt
Keyword(s):  
Protein Synthesis ◽  
Rat Liver ◽  
Liver Ribosomes

scholarly journals The Oxazolidinone Linezolid Inhibits Initiation of Protein Synthesis in Bacteria

1998 ◽  
Vol 42 (12) ◽  
pp. 3251-3255 ◽  
Author(s):  
Steve M. Swaney ◽  
Hiroyuki Aoki ◽  
M. Clelia Ganoza ◽  
Dean L. Shinabarger
Keyword(s):  
Protein Synthesis ◽  
Complex Formation ◽  
Antimicrobial Agents ◽  
Ribosomal Subunit ◽  
Multidrug Resistant ◽  
Binary Complex ◽  
Initiation Complex ◽  
Ribosomal Subunits ◽  
Bacterial Translation

ABSTRACT The oxazolidinones represent a new class of antimicrobial agents which are active against multidrug-resistant staphylococci, streptococci, and enterococci. Previous studies have demonstrated that oxazolidinones inhibit bacterial translation in vitro at a step preceding elongation but after the charging ofN-formylmethionine to the initiator tRNA molecule. The event that occurs between these two steps is termed initiation. Initiation of protein synthesis requires the simultaneous presence of N-formylmethionine-tRNA, the 30S ribosomal subunit, mRNA, GTP, and the initiation factors IF1, IF2, and IF3. An initiation complex assay measuring the binding of [3H]N-formylmethionyl-tRNA to ribosomes in response to mRNA binding was used in order to investigate the mechanism of oxazolidinone action. Linezolid inhibited initiation complex formation with either the 30S or the 70S ribosomal subunits fromEscherichia coli. In addition, complex formation withStaphylococcus aureus 70S tight-couple ribosomes was inhibited by linezolid. Linezolid did not inhibit the independent binding of either mRNA or N-formylmethionyl-tRNA toE. coli 30S ribosomal subunits, nor did it prevent the formation of the IF2–N-formylmethionyl-tRNA binary complex. The results demonstrate that oxazolidinones inhibit the formation of the initiation complex in bacterial translation systems by preventing formation of theN-formylmethionyl-tRNA–ribosome–mRNA ternary complex.

scholarly journals Differences in size, structure and function of free and membrane-bound polyribosomes of rat liver. Evidence for a single class of membrane-bound polyribosomes

1977 ◽  
Vol 168 (1) ◽  
pp. 1-8 ◽  
Author(s):  
J C Ramsey ◽  
W J Steele
Keyword(s):  
Protein Synthesis ◽  
Rat Liver ◽  
Size Structure ◽  
Large Fraction ◽  
Liver Homogenate ◽  
Structure And Function ◽  
Structural And Functional Properties ◽  
Membrane Bound ◽  
And Function

Free loosely bound and tightly bound polyribosomes were separated from rat liver homogenate by salt extraction followed by differential centrifugation, and several of their structural and functional properties were compared to resolve the existence of loosely bound polyribosomes and verify the specificity of the separation. The free and loosely bound polyribosomes have similar sedimentation profiles and polyribosome contents, their subunit proteins have similar electrophoretic patterns and their products of protein synthesis in vitro show a close correspondence in size and amounts synthesized. In contrast, the tightly bound polyribosomes have different properties from those of the free and loosely bound polyribosomes; their average size is significantly smaller; their polyribosome content is higher; their 60 S-subunit proteins lack two components and contain four or more components not found elsewhere; their products of protein synthesis in vitro differ in size and amounts synthesized. These observations show that rat liver membranes entrap a large fraction of the free polyribosomes at low salt concentrations and that these polyribosomes are similar to those of the free-polyribosome fraction and are different from those of the tightly bound polyribosome fraction in size, structure and function.

scholarly journals Biotin-mediated protein biosynthesis

1974 ◽  
Vol 140 (3) ◽  
pp. 549-556 ◽  
Author(s):  
R. L. Boeckx ◽  
K. Dakshinamurti
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Rat Liver ◽  
Intestinal Mucosa ◽  
Protein Biosynthesis ◽  
Amino Acid Incorporation ◽  
Acid Incorporation ◽  
Stimulation Of

The effect of administration of biotin to biotin-deficient rats on protein biosynthesis was studied. Biotin treatment resulted in stimulation by more than twofold of amino acid incorporation into protein, both in vivo and in vitro in rat liver, pancreas, intestinal mucosa and skin. Analysis of the products of amino acid incorporation into liver proteins in vivo and in vitro indicated that the synthesis of some proteins was stimulated more than twofold, but others were not stimulated at all. This indicates a specificity in the stimulation of protein synthesis mediated by biotin.

scholarly journals Inhibition of protein synthesis by ricin: experiments with rat liver mitochondria and nuclei and with ribosomes from Escherichia coli

1974 ◽  
Vol 142 (3) ◽  
pp. 695-697 ◽  
Author(s):  
Margherita Greco ◽  
Lucio Montanaro ◽  
Francesco Novello ◽  
Cecilia Saccone ◽  
Simonetta Sperti ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Protein Synthesis ◽  
Rat Liver ◽  
Ricinus Communis ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Isolated Rat Liver ◽  
Liver Nuclei ◽  
Isolated Rat ◽  
Liver Ribosomes

1. Ricin, a toxic protein from the seeds of Ricinus communis which inhibits poly(U)-directed polyphenylalanine synthesis by rat liver ribosomes (Montanaro et al., 1973), does not affect protein synthesis by isolated rat liver mitochondria. 2. The toxin is ineffective also on poly(U)-directed polyphenylalanine synthesis in reconstituted systems with ribosomes isolated from rat liver mitochondria or from Escherichia coli. 3. Ricin inhibits protein synthesis by isolated rat liver nuclei, but at concentrations much higher than those affecting rat liver ribosomes.

scholarly journals Inhibition by ricin of protein synthesis in vitro. Inhibition of the binding of elongation factor 2 and of adenosine diphosphate-ribosylated elongation factor 2 to ribosomes

1975 ◽  
Vol 146 (1) ◽  
pp. 127-131 ◽  
Author(s):  
L Montanaro ◽  
S Sperti ◽  
A Mattioli ◽  
G Testoni ◽  
F Stirpe
Keyword(s):  
Protein Synthesis ◽  
Binding Sites ◽  
Polypeptide Chain ◽  
Elongation Factor ◽  
Adenosine Diphosphate ◽  
Chain Elongation ◽  
Elongation Factor 2 ◽  
In Vitro Inhibition ◽  
Liver Ribosomes

The binding of EF2 (elongation factor 2) and of ADP-ribosyl-EF 2 to rat liver ribosomes is inhibited by ricin. This result suggests that the native enzyme and its ADP-ribose derivative have the same or closely related binding sites on the ribosome. The inhibition by ricin of the binding of EF 2 to ribosomes is consistent with the previous observation that ricin affects EF 2-catalysed translocation during polypeptide chain elongation.

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