Role of an RNA-binding protein in import of tRNA into Leishmania mitochondria.
Nuclear-encoded cytoplasmic tRNAs are imported into the mitochondria of kinetoplastid protozoa by an unknown mechanism. In a Leishmania in organello system, ATP-dependent import of a cloned, unspliced tRNATyr(GUA) transcript was demonstrated by protection from ribonuclease, whereas import of a tRNAGln(CUG) transcript was much less efficient. Specific binding of tRNATyr to two mitochondrial surface proteins of 15 and 22 kilodaltons was observed. Tubulin antisense-binding protein (TAB), the 15-kilodaton species, was purified to apparent homogeneity by RNA affinity chromatography. TAB forms stable complexes with the D stem-loop region of tRNATyr. Immunocytochemical and cell fractionation experiments, combined with limited proteolysis, suggested the association of TAB with the outer mitochondrial membrane. Importantly, anti-TAB antibody specifically inhibited binding as well as import of tRNATyr and of a synthetic structural homolog. These results support the role of TAB as a membrane-bound receptor or carrier for RNA import into Leishmania mitochondria.
Adhya
S
S
Genetic Engineering Laboratory, Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Calcutta 700032, India.
Ghosh
T
T
Das
A
A
Bera
S K
SK
Mahapatra
S
S
D000818:Animals; D001483:Base Sequence; D001692:Biological Transport; D002474:Cell-Free System; D007891:Leishmania / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D015800:Protozoan Proteins / Q000378:metabolism*; D016372:RNA, Antisense / Q000378:metabolism; D016053:RNA, Protozoan / Q000378:metabolism*; D012365:RNA, Transfer, Tyr / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D014404:Tubulin / Q000235:genetics
D008565:Membrane Proteins; D015800:Protozoan Proteins; D016372:RNA, Antisense; D016053:RNA, Protozoan; D012365:RNA, Transfer, Tyr; D016601:RNA-Binding Proteins; C107685:TAB protein, Leishmania donovani; D014404:Tubulin