This eukaryotic domain is found in ryanodine receptors (RyR) and inositol 1,4,5-trisphosphate receptors (IP3R) which together form a superfamily of homotetrameric ligand-gated intracellular Ca2+ channels [1]. There seems to be no known function for this domain [2]. Also see the IP3-binding domain Pfam:PF01365 and Pfam:PF02815.

1: What we don't know about the structure of ryanodine receptor calcium release channels. Dulhunty AF, Pouliquin P; Clin Exp Pharmacol Physiol 2003;30:713-723. PMID:14516409

2: Novel repeats in ryanodine and IP3 receptors and protein O-mannosyltransferases. Ponting CP; Trends Biochem Sci 2000;25:48-50. PMID:10664581