Nicotinic acid adenine dinucleotide phosphate (NAADP) binding protein required for NAADP-evoked intracellular calcium release. Confers NAADP-sensitivity to the two pore channels (TPCs) complex (By similarity). Enables NAADP to activate Ca(2+) release from the endoplasmic reticulum through ryanodine receptors (PubMed:33758062). Monomer. Dimer. Interacts with TPCN1. Colocalizes with type 1 ryanodine receptor (RYR1). Belongs to the JUPITER family.