ORAI-1 is a protein homolog of Drosophila Orai and human Orai1, Orai2 and Orai3. ORAI-1 GFP reporters are co- expressed with STIM-1 (ER CA(2+) sensors) in the gonad and intestine. The protein has four predicted transmembrane domains with a highly conserved region between TM2 ad TM3. This conserved domain is thought to function in channel regulation. ORAI1- related proteins are required for the production of the calcium channel, CRAC, along with STIM1-related proteins.