An RNA-binding Respiratory Component Mediates Import of Type II tRNAs into Leishmania Mitochondria

Chatterjee, Saibal and Home, Pratik and Mukherjee, Saikat and Mahata, Bidesh and Goswami, Srikanta and Dhar, Gunjan and Adhya, Samit (2006) An RNA-binding Respiratory Component Mediates Import of Type II tRNAs into Leishmania Mitochondria. The Journal of Biological Chemistry, 281 (35). pp. 25270-25277.


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    Transport of tRNAs across the inner mitochondrial membrane of the kinetoplastid protozoon Leishmania requires interactions with specific binding proteins (receptors) in a multi-subunit complex. The allosteric model of import regulation proposes cooperative and antagonistic interactions between two or more receptors with binding specificities for distinct tRNA families (types I and II, respectively). To identify the type II receptor, the gene encoding RIC8A, a subunit of the complex, was cloned. The C-terminal region of RIC8A is homologous to subunit 6b of ubiquinol cytochrome c reductase (respiratory complex III), while the N-terminal region has intrinsic affinity for type II, but not for type I, mtRNAs. RIC8A is shared by the import complex and complex III, indicating its bi-functionality, but is assembled differently in the two complexes. Knockdown of RIC8A in Leishmania lowered the mitochondrial content of type II tRNAs but raised that of type I tRNAs, with downstream effects on mitochondrial translation and respiration, and cell death. In RIC8A knockdown cells, a subcomplex was formed that interacted with type I tRNA, but the negative regulation by type II tRNA was lost. Mitochondrial extracts from these cells were defective for type II, but not type I, import; import and regulation were restored by purified RIC8A. These results provide evidence for the relevance of allosteric regulation in vivo and indicate that acquisition of new tRNA-binding domains by ancient respiratory components have played a key role in the evolution of mitochondrial tRNA import. Mitochondria from

    Item Type: Article
    Subjects: Molecular & Human Genetics
    Divisions: Indian Institute of Chemical Biology
    Depositing User: Mr Shyamal Nath
    Date Deposited: 02 Nov 2011 14:00
    Last Modified: 03 Feb 2012 11:36
    Official URL: htpp://

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