“Active Transport of Divalent Cations by the Plasma Membrane Calcium Pump”.

”. ONTIVEROS MALLKU; MANGIALAVORI IRENE C., ROSSI JUAN PABLO F.C.; FERREIRA GOMES MARIELA

Tucumán

Congreso; XLI Reunión Anual de la Sociedad Argentina de Biofísica (SAB).; 2012

Sociedad Argentina de Biofísica

“Active Transport of Divalent Cations by the Plasma Membrane Calcium Pump”. Ontiveros Mallku; Mangialavori Irene C., Rossi Juan Pablo F.C.; Ferreira‑Gomes Mariela. Libro de Resúmenes: Pag 92. The plasma membrane calcium pump (PMCA) is widely distributed along the eukaryotic cells. This pump transports Ca2+ actively from cytoplasm to extracellular medium coupled to the hydrolysis of ATP maintaining a low intracellular concentration of this cation. PMCA is mainly regulated by the Ca2+-calmodulin complex (Ca2+-CaM). In the absence of CaM the pump is auto-inhibited; while binding of CaM to the C-terminal domain produces the activation of the pump1. The aim of this work is to study the transport of several divalent cations (C2+) by PMCA in both auto-inhibited and activated state. Purified PMCA preparations and inside-out vesicles (IOVS) were obtained from human erythrocytes membranes. We measured the C2+-ATPase activity as function of Ca2+, Sr2+, Ba2+ and Pb2+, in the presence and absence of CaM as well as, with the enzyme previously activated by removing the C-terminal domain with chymotrypsin2. Additionally, we study the active transport of divalent cations into IOVS by measuring light scattering changes of the vesicles. Our results show that: (a) PMCA is able to transport divalent cations other than Ca2+; (b) These cations are transported with different affinities and velocities; (c) PMCA activated state presents an increased affinity for the studied cations; (d) Both C2+-ATPase and transport of C2+ measured by light scattering show a similar behavior revealing that both processes are coupled.