Import of RNA into Leishmania mitochondria occurs through direct interaction with membrane-bound receptors.
Cytoplasmic tRNAs are imported into the kinetoplast mitochondrion of Leishmania, but the mechanism of import is unknown, particularly whether RNA is transferred as a ribonucleoprotein complex through the protein import pathway or by a distinct receptor-mediated mechanism. Using isolated mitochondria, it was shown that a small, importable RNA, which is structurally homologous to tRNA, binds rapidly, specifically, and with high affinity to the mitochondrial surface in the absence of soluble protein factors to form an import intermediate. Two classes of binding site of apparent Kd 0.3 and 10 n, respectively, were distinguished. tRNA from Leishmania, but not yeast, competitively inhibited the binding. Northwestern blot analysis revealed the presence of a 15-kDa RNA binding protein on the mitochondrial surface. Whereas receptor binding was resistant to heparin and KCl, internalization was sensitive to both reagents. These results are consistent with the presence of a direct mechanism of receptor-mediated RNA import on Leishmania mitochondria.
Mahapatra
S
S
Genetic Engineering Laboratory, Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Calcutta 700032, India.
Adhya
S
S
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D001667:Binding, Competitive; D001692:Biological Transport; D002451:Cell Compartmentation; D002474:Cell-Free System; D006493:Heparin / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism; D007891:Leishmania / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009994:Osmolar Concentration; D000071228:Polyelectrolytes; D011108:Polymers / Q000494:pharmacology; D016053:RNA, Protozoan / Q000378:metabolism*; D012343:RNA, Transfer / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D014404:Tubulin / Q000235:genetics
D000255:Adenosine Triphosphate; D006493:Heparin; D000071228:Polyelectrolytes; D011108:Polymers; D016053:RNA, Protozoan; D012343:RNA, Transfer; D018160:Receptors, Cytoplasmic and Nuclear; D014404:Tubulin