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"Ping-pong" interactions between mitochondrial tRNA import receptors within a multiprotein complex.

Authors
  • Bhattacharyya, Subhendra Nath
  • Chatterjee, Saibal
  • Goswami, Srikanta
  • Tripathi, Gayatri
  • Dey, Sailendra Nath
  • Adhya, Samit
Type
Published Article
Journal
Molecular and cellular biology
Publication Date
Aug 01, 2003
Volume
23
Issue
15
Pages
5217–5224
Identifiers
PMID: 12861008
Source
Medline
License
Unknown

Abstract

The mitochondrial genomes of a wide variety of species contain an insufficient number of functional tRNA genes, and translation of mitochondrial mRNAs is sustained by import of nucleus-encoded tRNAs. In Leishmania, transfer of tRNAs across the inner membrane can be regulated by positive and negative interactions between them. To define the factors involved in such interactions, a large multisubunit complex (molecular mass, approximately 640 kDa) from the inner mitochondrial membrane of the kinetoplastid protozoon Leishmania, consisting of approximately 130-A particles, was isolated. The complex, when incorporated into phospholipid vesicles, induced specific, ATP- and proton motive force-dependent transfer of Leishmania tRNA(Tyr) as well as of oligoribonucleotides containing the import signal YGGYAGAGC. Moreover, allosteric interactions between tRNA(Tyr) and tRNA(Ile) were observed in the RNA import complex-reconstituted system, indicating the presence of primary and secondary tRNA binding sites within the complex. By a combination of antibody inhibition, photochemical cross-linking, and immunoprecipitation, it was shown that binding of tRNA(Ile) to a 21-kDa component of the complex is dependent upon tRNA(Tyr), while binding of tRNA(Tyr) to a 45-kDa component is inhibited by tRNA(Ile). This "ping-pong" mechanism may be an effective means to maintain a balanced tRNA pool for mitochondrial translation.

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