Conformational changes during the reaction cycle of plasma membrane Ca2+-ATPase in the autoinhibited and activated states

NICOLAS ANDRÉS SAFFIOTI; MARILINA DE SAUTU; ANA SOL RIESCO; MARIELA FERREIRA -GOMES; JUAN PABLO ROSSI; IRENE C MANGIALAVORI

BIOCHEMICAL JOURNAL

PORTLAND PRESS LTD

Lugar: Londres; Año: 2021 vol. 478 p. 2019 - 2034

0264-6021

Plasma membrane Ca2+-ATPase (PMCA) transports Ca2+ by a reaction cycle including phosphorylated intermediates. Calmodulin binding to the C-terminal tail disrupts autoinhibitory interactions, activating the pump. To assess the conformational changes during the reaction cycle, we studied the structure of different PMCA states using a fluorescent probe, hydrophobic photolabeling, controlled proteolysis and Ca2+-ATPase activity.Our results show that calmodulin binds to E2P-like states, and during dephosphorylation, the hydrophobicity in the nucleotide-binding pocket decreases and the Ca2+ binding site becomes inaccessible to the extracellular medium. Autoinhibitory interactions are disrupted in E1Ca and in the E2P ground state whereas they are stabilized in the E2∙Pi product state. Finally, we propose a model that describes the conformational changes during the Ca2+ transport of PMCA.