Structure of a sodium-ion/calcium-ion exchanger
Youxing Jiang group (University of Texas - Southwestern)
Youxing Jiang's group from UT-Southwestern provided a
highlight on Na+/Ca2+ exchangers (NCX), which are
membrane transporters that maintain the homeostasis of cytosolic
Ca2+ and play an essential role in Ca2+ signaling.
Despite a long history of physiological work and a large body of functional
data, the structural basis underlying the ion exchange mechanism of NCX is
poorly understood, and the exchanger field long sought an atomic description
of an NCX protein. In this study, the Jiang group presented the first
high-resolution (1.9 Å) crystal structure of a
Na+/Ca2+ exchanger from Methanococcus jannaschii,
NCX_Mj, and demonstrated that this archaeal NCX catalyzes
Na+/Ca2+ exchange reactions similar to its eukaryotic
counterpart. The high-resolution structure reveals much about the mechanism
of Na+/Ca2+ exchange in NCX proteins and also explains
the stoichiometry, cooperativity and bi-directionality of the ion exchange
reaction in NCX.
Figure: Crystal structure of the
Na+/Ca2+ exchanger embedded in a membrane bilayer.
Liao, J, Li, H, Zeng, W, Sauer, DB, Belmares, R, Jiang, Y. Structural
insight into the ion-exchange mechanism of the sodium/calcium exchanger,
Science 335, 686-690 (2012).