Characterization of the plasma-membrane calcium pump from Trypanosoma cruzi

Abstract

Despite previous reports suggesting that the plasma-membrane Ca2+-ATPases of different trypanosomatids differ from the Ca2+ pumps present in mammalian cells, Trypanosoma cruzi plasma-membrane Ca2+-ATPase shares several characteristics with the Ca2+ pumps present in other systems. This enzyme could be partially purified from epimastigote plasma-membrane vesicles using calmodulin-agarose affinity chromatography. The activity of the partially purified enzyme was stimulated by T. cruzi or bovine brain calmodulin. In addition, the enzyme cross-reacted with antiserum and monoclonal antibody 5F10 raised against human red-blood-cell Ca2+-ATPase, has a molecular mass of 140 kDa and forms Ca2+-dependent hydroxylamine-sensitive phosphorylated intermediates. These results, together with its high sensitivity to vanadate, indicate that this enzyme belongs to the P-type class of ionic pumps.