An RNA-binding respiratory component mediates import of type II trnas into Leishmania mitochondria

Chatterjee, Saibal ; Home, Pratik ; Mukherjee, Saikat ; Mahata, Bidesh ; Goswami, Srikanta ; Dhar, Gunjan ; Adhya, Samit (2006) An RNA-binding respiratory component mediates import of type II trnas into Leishmania mitochondria Journal of Biological Chemistry, 281 (35). pp. 25270-25277. ISSN 0021-9258

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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, tRNAs. 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.

Item Type:Article
Source:Copyright of this article belongs to American Society for Biochemistry and Molecular Biology.
ID Code:12105
Deposited On:10 Nov 2010 04:31
Last Modified:16 May 2016 21:30

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