How Ca(2+) permeates the Orai1 channel and the mechanism by which the channel achieves high Ca(2+) selectivity remain critical questions in understanding store-operated Ca(2+) influx. In research published in Science Signaling, Frischauf et al. identified a Ca(2+)-accumulating region (CAR) in the extracellular opening of Orai1, which explains how concentrating Ca(2+) at the mouth of Orai1 facilitates channel permeation and contributes to selectivity.
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