INTERACTION OF SMALL RIBOSOMAL AND TRANSFER-RNAS WITH A PROTEIN FROM LEISHMANIA-DONOVANI

Using synthetic antisense RNA from the 5'-untranslated region of the b eta-tubulin gene as probe in gel retardation assays, a heat stable RNA -binding factor was identified in promastigotes of the kinetoplastid p rotozoan Leishmania donovani. The same or similar factors interact wit h several small ribosomal RNA (srRNA) species and, more weakly, with t RNA, as shown by binding and competition experiments. Deletion analysi s indicated involvement of repeated purine-rich motifs on the antisens e RNA, in the reaction. Related, conserved motifs occur on at least tw o of the srRNAs. By a modified Western blot assay, the RNA-binding spe cies was identified as a single, small polypeptide. The activity is ap parently specific for the promastigote stage of the parasite, being un detectable in amastigotes. The properties of this RNA-binding factor s uggest that it is a novel, previously uncharacterised protein.