This domain is found in the transient receptor ion channel (Trp) family of proteins. There is strong evidence that Trp proteins are structural elements of calcium-ion entry channels activated by G protein-coupled receptors [1]. This domain does not tend to appear with the TRP domain (Pfam:PF06011) but is often found to the C-terminus of Ankyrin repeats (Pfam:PF00023).

1: Mouse trp2, the homologue of the human trpc2 pseudogene, encodes mTrp2, a store depletion-activated capacitative Ca2+ entry channel. Vannier B, Peyton M, Boulay G, Brown D, Qin N, Jiang M, Zhu X, Birnbaumer L; Proc Natl Acad Sci U S A 1999;96:2060-2064. PMID:10051594