STIM1 (stromal interacting molecule 1) coordinates store-operated Ca (2+) entry (SOCE) and acts as a Ca (2+) sensor in the endoplasmic reticulum. Upon Ca (2+) depletion, STIM1 translocates to the plasma membrane and activates the Ca (2+) -releasing activated Ca (2+) (CRAC) channel subunit ORAI1. STIM1 Protein, Human (HEK293, His) is the recombinant human-derived STIM1 protein, expressed by HEK293 , with C-His labeled tag.