EF-Hand Calcium Binding Domain Protein 4B (EFCAB4B)

EFCAB4B, Contains 2 EF-hand domains. Interacts with ORAI1 and STIM1; the interaction is direct and takes place in absence of Ca²⁺. Forms a complex with ORAI1 and STIM1 at low concentration of Ca²⁺, the complex dissociates at elevated Ca²⁺ concentrations. Ca²⁺-binding protein that plays a key role in store-operated Ca²⁺ entry in T-cells by regulating CRAC channel activation. Acts as a cytoplasmic calcium-sensor that facilitates the clustering of ORAI1 and STIM1 at the junctional regions between the plasma membrane and the endoplasmic reticulum upon low Ca²⁺ concentration. It thereby regulates CRAC channel activation, including translocation and clustering of ORAI1 and STIM1. Upon increase of cytoplasmic Ca²⁺ resulting from opening of CRAC channels, dissociates from ORAI1 and STIM1, thereby destabilizing the ORAI1-STIM1 complex.