IP3 binds to the IP3 receptor, opening the endoplasmic reticulum Ca2+ channel Authored: Le Novere, N, Jassal, B, 2004-03-31 12:22:05 Edited: Jassal, B, 2006-10-10 09:20:18 Reactome Database ID Release 43169680 Reactome, http://www.reactome.org ReactomeREACT_12008 Reviewed: Gillespie, ME, 2009-06-02 00:56:21 The IP3 receptor (IP3R) is an IP3-gated calcium channel. It is a large, homotetrameric protein, similar to other calcium channel proteins such as ryanodine. The four subunits form a 'four-leafed clover' structure arranged around the central calcium channel. Binding of ligands such as IP3 results in conformational changes in the receptor's structure that leads to channel opening. has a Stoichiometric coefficient of 4 IP3 receptor homotetramer IP3 receptor:IP3 complex