Affinity labeling the ribosome with eukaryotic-specific antibiotics: (bromoacetyl)trichodermin.

Area of Science:

• Molecular Biology
• Biochemistry
• Cell Biology

Background:

• Trichodermin is a eukaryotic-specific antibiotic that inhibits protein synthesis.
• Understanding the precise molecular targets of antibiotics is crucial for drug development and resistance studies.

Purpose of the Study:

• To identify the specific ribosomal proteins that interact with trichodermin in Drosophila cells.
• To map the binding site of trichodermin on the ribosome and understand its mechanism of action.

Main Methods:

• Synthesis of a 14C-labeled bromoacetyl derivative of trichodermin.
• Covalent labeling of Drosophila 80S ribosomes and subsequent identification of labeled proteins.
• Competition assays with unmodified trichodermin to confirm native binding site interaction.
• Affinity labeling with puromycin to identify A and P site interactions.

Main Results:

• [14C] (bromoacetyl)trichodermin covalently labeled six ribosomal proteins: L1, L3, L24 (large subunit) and S3/S5, 2/3S, S8 (small subunit).
• Labeling was specific to the native trichodermin binding site, as shown by competition experiments.
• Protein S8 was labeled in the A site, and S3/S5 in the P site, suggesting the binding site spans both sites.

Conclusions:

• The trichodermin binding site on Drosophila ribosomes involves multiple proteins from both the large and small subunits.
• The binding site appears to encompass portions of both the ribosomal A and P sites.
• These findings contribute to a model of protein locations within the ribosome's active site.