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Peptidyl transferase of bacterial ribosome: resistance to proteinase K
Abstract:
70-S ribosomes and 50-S ribosomal subunits from Escherichia coli D10 were treated with proteinase K for increasing periods of time. Peptidyl transferase activity and sparsomycin-induced binding of (U)C-A-C-C-A-[3H]Leu-Ac were tested in the treated particles, the binding of the substrate being more sensitive to the protease than peptide bond formation. Comparison of the amounts of proteins present in the treated particles with the residual activity indicates that only proteins L3 and L14 are released at a similar rate to that at which peptidyl transferase activity is lost. Proteins related to this ribosomal activity by other techniques are lost at a faster rate than the activity itself. In addition, the results indicate that sparsomycin stimulates the binding of the substrate by a different mechanism from that which inhibits peptide bond formation.
Insights
Proteinase K treatment of Escherichia coli ribosomes reveals that proteins L3 and L14 are crucial for peptidyl transferase activity. Sparsomycin affects substrate binding and peptide bond formation via distinct mechanisms.
Area of Science:
- Molecular Biology
- Biochemistry
- Ribosome Function
Background:
- Escherichia coli 70S ribosomes and 50S ribosomal subunits are essential for protein synthesis.
- Understanding the specific protein components responsible for peptidyl transferase activity is key to deciphering ribosomal function.
- Investigating the mechanisms of action for antibiotics like sparsomycin is crucial for drug development.
Purpose of the Study:
- To identify the ribosomal proteins essential for peptidyl transferase activity in E. coli.
- To determine the sensitivity of peptidyl transferase activity and substrate binding to proteolytic degradation.
- To elucidate the distinct mechanisms by which sparsomycin influences substrate binding and peptide bond formation.
Main Methods:
- Treatment of E. coli 70S ribosomes and 50S subunits with proteinase K for varying durations.
- Assay of peptidyl transferase activity in treated ribosomal particles.
- Measurement of sparsomycin-induced binding of a labeled substrate analog ((U)C-A-C-C-A-[3H]Leu-Ac).
- Quantification of remaining ribosomal proteins after protease treatment.
Main Results:
- Peptidyl transferase activity and sparsomycin-induced substrate binding were assessed in proteinase K-treated ribosomes.
- Substrate binding was found to be more sensitive to protease treatment than peptide bond formation.
- Proteins L3 and L14 were released at a rate comparable to the loss of peptidyl transferase activity.
- Other proteins implicated in ribosomal activity were degraded faster than the loss of activity.
- Sparomycin was shown to stimulate substrate binding through a mechanism different from its inhibition of peptide bond formation.
Conclusions:
- Ribosomal proteins L3 and L14 are critical for maintaining peptidyl transferase activity in E. coli ribosomes.
- The binding of substrates to ribosomes and the catalytic formation of peptide bonds exhibit differential sensitivity to proteolysis.
- Sparsomycin employs distinct molecular mechanisms to modulate substrate binding and inhibit peptide bond formation, highlighting its complex interaction with the ribosome.