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Puromycin inhibition of eucaryotic ribosomes. Differences in sensitivity between polypeptide synthesis directed by
Abstract:
In a protein synthesis sytem derived from porcine uteri we have made the following observations: 1. Synthesis directed by the endogenous mRNA of the system is more sensitive to inhibition by puromycin than poly(U) directed synthesis. 2. Synthesis directed by the synthetic templates poly(G,U) and poly(C,U) is more sensitive to inhibition by puromycin than poly(U) directed synthesis and frequently shows a sensitivity to puromycin similar to that directed by endogenous mRNA. 3. Protein synthesis was inhibited by three aminoacyloligonucleotides (C-A-Phe, C-A-Asp, and C-A-Pro) which are analogs of the 3' terminus of aminoacyl tRNAs. Of the three, C-A-Phe was the most active and C-A-Asp the least active but, unlike puromycin, inhibition by these compounds was the same for endogenous and poly(U) directed synthesis. These results are interpreted as supporting the proposal that the acceptor site of ribosomes contains an hydrophobic binding region which interacts with the side chain of aliphatic amino acids, and particularly with the aromatic side chain of phenylalanine.
Insights
Puromycin sensitivity in protein synthesis differs between endogenous mRNA and synthetic templates. Aminoacyl-oligonucleotides also inhibit protein synthesis, suggesting a hydrophobic binding region on ribosomes interacting with amino acid side chains, especially phenylalanine.
Area of Science:
- Biochemistry
- Molecular Biology
- Protein Synthesis
Background:
- Protein synthesis is a fundamental biological process involving ribosomes and mRNA templates.
- Puromycin is an antibiotic that inhibits protein synthesis by acting as a chain terminator.
- Aminoacyl-tRNAs deliver specific amino acids to the ribosome during translation.
Purpose of the Study:
- To investigate the differential sensitivity of protein synthesis to puromycin inhibition.
- To explore the effect of aminoacyl-oligonucleotides on protein synthesis directed by various templates.
- To elucidate the structural features of the ribosomal acceptor site.
Main Methods:
- Utilized a protein synthesis system derived from porcine uteri.
- Compared puromycin inhibition of endogenous mRNA-directed and synthetic template-directed (poly(U), poly(G,U), poly(C,U)) protein synthesis.
- Tested the inhibitory effects of aminoacyl-oligonucleotides (C-A-Phe, C-A-Asp, C-A-Pro) on protein synthesis.
Main Results:
- Endogenous mRNA-directed synthesis was more sensitive to puromycin than poly(U)-directed synthesis.
- Poly(G,U) and poly(C,U) directed synthesis showed puromycin sensitivity similar to endogenous mRNA.
- Aminoacyl-oligonucleotides inhibited protein synthesis, with C-A-Phe being the most potent; inhibition was consistent across endogenous and poly(U) directed synthesis.
Conclusions:
- Ribosomal acceptor site likely possesses a hydrophobic region interacting with amino acid side chains.
- Phenylalanine's aromatic side chain appears to have a significant interaction with this hydrophobic binding region.