It's All in the Symmetry

Calcium ion (Ca2+) signaling is essential to many cellular processes, from fertilization to apoptosis (cell death). Stable Ca2+ levels are achieved through tightly regulated and coordinated cellular processes. Alterations in Ca2+ levels are involved in many pathological conditions, including stroke and heart failure ( 1 ). After Ca2+ stimulation, the Na+/Ca2+ exchanger (NCX)—a ubiquitous Ca2+ export protein residing in the plasma membrane—participates in the restoration of resting levels of Ca2+ in excitable cells. On page 686 of this issue, Liao et al. ( 2 ) report the structure of a prokaryotic homolog of NCX, revealing a symmetrical protein scaffold and ion-binding pocket that provides detailed insights into the Na+/Ca2+ exchange process.