Fig. 2.

Topology model of transient receptor potential melastatin 2 (Trpm2) channel. Trpm2 monomer is depicted as having 6 transmembrane domains (S1 to S6) with the putative pore-forming loop situated between S5 and S6. Four monomers associate to form a functional Trpm2 channel. Both N- and C-termini are in the cytosol. The N-terminus contains 4 sections of Trpm subfamily homology domain (MHD). In the second MHD, there is an IQ-like motif which binds Ca²⁺-calmodulin. The C-terminus contains a Trp box (TRP), a coiled-coil domain (CCD), and the adenosine diphosphate ribose (ADPR) pyrophosphatase homolog domain (NUDIX). Trpm2 is a non-specific cation-permeable channel which allows entry of Ca²⁺, Na⁺, and K⁺.