Context-specific inhibition of mitochondrial ribosomes by phenicol and oxazolidinone antibiotics

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Antibiotics chloramphenicol (CHL) and oxazolidinones (e.g., linezolid, LZD) inhibit mitochondrial translation, leading to severe side effects.
• The precise mechanism of CHL and LZD action on mitochondrial ribosomes remains largely unexplored, unlike their well-understood bacterial ribosome inhibition.

Purpose of the Study:

• To investigate the context-specific mechanism of mitochondrial ribosome inhibition by CHL and LZD.
• To elucidate the structural basis of linezolid's interaction with the human mitochondrial ribosome.

Main Methods:

• Mitoribosome profiling to identify sequences causing ribosome stalling.
• In vitro translation assays to validate context-specific inhibition.
• High-resolution cryo-electron microscopy (cryo-EM) to determine the structure of linezolid bound to the human mitoribosome.

Main Results:

• CHL and LZD induce mitochondrial ribosome stalling in a context-specific manner, primarily at sequences with alanine, serine, or threonine in the penultimate position.
• In vitro assays confirmed this context-dependent stalling.
• Cryo-EM revealed that LZD binds to the human mitochondrial ribosomal peptidyl transfer center (PTC) similarly to its binding in bacterial ribosomes.

Conclusions:

• Mitochondrial ribosome inhibition by CHL and LZD is sequence-context specific, similar to bacterial inhibition.
• Structural insights into LZD-mitoribosome interaction offer potential for designing less toxic antibiotics.
• Findings may inform the development of novel antibiotics with improved safety profiles to combat antimicrobial resistance.