ISOLATION AND CHARACTERIZATION OF LEISHMANIA-DONOVANI CALRETICULIN GENE AND ITS CONSERVATION OF THE RNA-BINDING ACTIVITY

Calreticulin has been implicated in multiple cell functions. Recently, we have shown that both human and simian calreticulin are RNA binding proteins and that their binding activity is due to phosphorylation. T o demonstrate that the RNA binding property of calreticulin is an intr insic part of this multi-functional molecule and is evolutionarily con served, we isolated and characterized the calreticulin gene from the u nicellular parasite, Leishmania donovani. Amino acid sequence homology between human and Leishmania calreticulin (L. d. cal) is limited, but like the human homologue, L. d. cal binds Ca++, can be phosphorylated in vitro and binds certain RNA sequences in a phosphorylation-depende nt manner. Unlike human calreticulin, L. d. cal is glycosylated and it s binding to endogenous Leishmania RNA is phosphorylation-independent. The binding of L. d. cal to Leishmania RNA suggests that the RNA bind ing activity of calreticulin has remained evolutionarily conserved.