title: "Ping-pong" interactions between mitochondrial tRNA import receptors within a multiprotein complex.
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.
authors.affiliation: Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Calcutta 700032, India.
authors.forename: Subhendra Nath
authors.initials: SN
authors.lastname: Bhattacharyya
authors.forename: Saibal
authors.initials: S
authors.lastname: Chatterjee
authors.forename: Srikanta
authors.initials: S
authors.lastname: Goswami
authors.forename: Gayatri
authors.initials: G
authors.lastname: Tripathi
authors.forename: Sailendra Nath
authors.initials: SN
authors.lastname: Dey
authors.forename: Samit
authors.initials: S
authors.lastname: Adhya
mesh_terms: D000495:Allosteric Site; D020816:Amino Acid Motifs; D000818:Animals; D015153:Blotting, Western; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005990:Glycerol / Q000378:metabolism; D007150:Immunohistochemistry; D007425:Intracellular Membranes / Q000378:metabolism; D007700:Kinetics; D007891:Leishmania / Q000378:metabolism*; D008027:Light; D008854:Microscopy, Electron; D008928:Mitochondria / Q000378:metabolism*; D008954:Models, Biological; D010743:Phospholipids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D014176:Protein Biosynthesis; D012343:RNA, Transfer / Q000378:metabolism*
chemical_list: D003432:Cross-Linking Reagents; D010743:Phospholipids; D012343:RNA, Transfer; D005990:Glycerol