title: A bifunctional tRNA import receptor from Leishmania mitochondria.
abstract: In kinetoplastid protozoa, import of cytosolic tRNAs into mitochondria occurs through tRNAs interacting with membrane-bound proteins, the identities of which are unknown. The inner membrane RNA import complex of Leishmania tropica contains multiple proteins and is active for import in vitro. RIC1, the largest subunit of this complex, is structurally homologous to the conserved alpha subunit of F1 ATP synthase. The RIC1 gene complemented an atpA mutation in Escherichia coli. Antisense-mediated knockdown of RIC1/F1alpha in Leishmania resulted in depletion of several mitochondrial tRNAs belonging to distinct subsets (types I and II) that interact cooperatively or antagonistically within the import complex. The knockdown-induced defect in import of type I tRNAs was rectified in a reconstituted system by purified RIC1/F1alpha alone, but recovery of type II tRNA import additionally required a type I tRNA. RIC1/F1alpha formed stable complexes with type I, but not type II, tRNAs through the cooperation of its nucleotide binding and C-terminal domains. Thus, RIC1/F1alpha is a type I tRNA import receptor. As expected of a bifunctional protein, RIC1/F1alpha is shared by both the import complex and by respiratory complex V. Alternative use of ancient respiratory proteins may have been an important step in the evolution of tRNA import.
authors.affiliation: Genetic Engineering Laboratory, Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Calcutta 700032, India.
authors.forename: Srikanta
authors.initials: S
authors.lastname: Goswami
authors.forename: Gunjan
authors.initials: G
authors.lastname: Dhar
authors.forename: Saikat
authors.initials: S
authors.lastname: Mukherjee
authors.forename: Bidesh
authors.initials: B
authors.lastname: Mahata
authors.forename: Saibal
authors.initials: S
authors.lastname: Chatterjee
authors.forename: Pratik
authors.initials: P
authors.lastname: Home
authors.forename: Samit
authors.initials: S
authors.lastname: Adhya
mesh_terms: D000818:Animals; D001692:Biological Transport; D007895:Leishmania tropica / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012343:RNA, Transfer / Q000378:metabolism*; D040681:Structural Homology, Protein
chemical_list: D021122:Protein Subunits; D015800:Protozoan Proteins; D012343:RNA, Transfer