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"Ping-pong" interactions between mitochondrial tRNA import receptors within a multiprotein complex.
Subhendra Nath Bhattacharyya1, Saibal Chatterjee, Srikanta Goswami
1Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Calcutta 700032, India.
Molecular and Cellular Biology
|July 16, 2003
Summary
Mitochondria import nucleus-encoded tRNAs for translation. A Leishmania mitochondrial complex facilitates tRNA import via a "ping-pong" mechanism, balancing tRNA pools for efficient protein synthesis.
Area of Science:
- Mitochondrial biology
- Molecular genetics
- Parasitology
Background:
- Mitochondrial genomes often lack sufficient transfer RNA (tRNA) genes, necessitating the import of nucleus-encoded tRNAs for mitochondrial messenger RNA (mRNA) translation.
- In Leishmania, the regulation of tRNA import across the inner mitochondrial membrane involves complex interactions.
Purpose of the Study:
- To identify and characterize the factors responsible for regulating tRNA import into Leishmania mitochondria.
- To elucidate the mechanism governing the interactions between imported tRNAs within the mitochondrial import machinery.
Main Methods:
- Isolation of a large multisubunit complex (approx. 640 kDa) from the inner mitochondrial membrane of Leishmania.
- Reconstitution of the complex into phospholipid vesicles to study its function.
- Utilized antibody inhibition, photochemical cross-linking, and immunoprecipitation to analyze protein-RNA interactions.
Main Results:
- The isolated complex mediated ATP- and proton motive force-dependent transfer of Leishmania tRNA(Tyr) and specific import signal-containing oligonucleotides.
- Allosteric interactions between tRNA(Tyr) and tRNA(Ile) were observed, suggesting distinct binding sites within the complex.
- A "ping-pong" mechanism was identified where tRNA(Ile) binding to a 21-kDa component depends on tRNA(Tyr), and tRNA(Tyr) binding to a 45-kDa component is inhibited by tRNA(Ile).
Conclusions:
- A novel multisubunit complex in Leishmania mitochondria regulates tRNA import.
- This complex employs a "ping-pong" mechanism involving interdependent tRNA binding to maintain a balanced tRNA pool essential for mitochondrial translation.