Calcium Release Activated Calcium Modulator 1 (CRACM1)

Calcium release-activated calcium channel protein 1 is a calcium selective ion channel. Orai1 channels play important role in the activation of T-lymphocytes. The loss of function mutation of Orai1 causes severe combined immunodeficiency (SCID) in humans The mammalian orai family has two additional homologs, orai2 and orai3.

Orai proteins share no homology with any other ion channel family of any other known proteins. They have 4 transmembrane domains and form tetramers. Orai channels are activated upon the depletion of internal calcium stores, which is called the "store-operated" or the "capacitative" mechanism. They are molecular constituents of the "calcium release activated calcium currents" (ICRAC).