Divalent metal ions transport by Plasma Membrane Calcium ATPase. Effect on regulation and selectivity

MALLKU ONTIVEROS; IRENE MANGIALAVORI; JORGE MARTIARENA; JUAN PABLO ROSSI; MARIELA FERREIRA-GOMES

Congreso; XLII. Reunión Anual de la Sociedad Argentina de Biofísica; 2013

The plasma membrane calcium pump(PMCA) transports Ca2+ actively to the extracellular medium coupled to the ATP hydrolysis maintaining the cellular homeostasis. PMCA is activated by interaction with Ca2+-calmodulin complex or by acidic phospholipids, increasing its affinity for Ca2+ and its maximum velocity [1, 2]. The aim of this work was to study the transport of different divalent cations that could be transported by PMCA, the effect on regulation and the selectivity of the pump. We assay the alkaline metals Be2+, Ca2+, Sr2+ and Ba2+, and Co2+, Cd2+ and Pb2+ from the fourth, fifth and sixth periods. The experiments were performed with both IOVs and the purified enzyme isolated from membranes of human erythrocytes. Results show that: (a) PMCA is able to transport Ca2+, Sr2+, Ba2+, Co2+ and Pb2+ with different capacity and affinity while Be2+ and Cd2+ are not transported; (b) PMCA activated by calmodulin shows an increased affinity for those cations; (c) there is a relation between the ionic radii of cations and the transport capability of the pump. These results suggest that the mechanism of expulsion of Ca2+ mediated by PMCA would also transport other divalent cations and that the size of such cation must be optimal for the interaction with the binding site of the enzyme. With grants of ANPCYT, CONICET and UBACYT   1- Mangialavori y col. J Biol Chem. 2009. 4823 2- Filomatoriy col. J Biol Chem. 2003. 22265