CHARACTERIZATION OF THE PLASMA-MEMBRANE CALCIUM-PUMP FROM TRYPANOSOMA-CRUZI

Despite previous reports [McLaughlin (1985) Mel. Biochem. Parasitol. 1 5, 189-201; Ghosh, Ray, Sarkar and Bhaduri (1990) J. Biol. Chem. 265, 11345-11351; Mazumder, Mukherjee, Ghosh, Ray and Bhaduri (1992) J. Bio l. Chem. 267, 18440-18446] suggesting that the plasma-membrane Ca2+-AT Pases of different trypanosomatids differ from the Calf pumps present in mammalian cells, Trypanosoma cruzi plasma-membrane Ca2+-ATPase shar es several characteristics with the Ca2+ pumps present in other system s. This enzyme could be partially purified from epimastigote plasma-me mbrane vesicles using calmodulin-agarose affinity chromatography. The activity of the partially purified enzyme was stimulated by T. cruzi o r 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+-depen dent hydroxylamine-sensitive phosphorylated intermediates. These resul ts, together with its high sensitivity to vanadate, indicate that this enzyme belongs to the P-type class of ionic pumps.