This family includes the N-terminus of the actin-interacting protein sperm-specific antigen 2, or KRAP (Ki-ras-induced actin-interacting protein). This region is found to be the residues that interact with inositol 1,4,5-trisphosphate receptor (IP3R). KRAP was first localized as a membrane-bound form with extracellular regions suggesting it might be involved in the regulation of filamentous actin and signals from the outside of the cells. It has now been shown to be critical for the proper subcellular localization and function of IP3R. Inositol 1,4,5-trisphosphate receptor functions as the Ca2+ release channel on specialized endoplasmic reticulum membranes, so the subcellular localization of IP3R is crucial for its proper function.
Jiyao W et al.(2023). "The conserved domain database in 2023.",