Fig. 2.

Predicted structural topology of TRP channels. All TRP channels contain 6 transmembrane segments (S1 to S6) with a putative pore region (P) between S5 and S6. NH₂- and COOH-termini are variable in length and contain different sets of domains. There are 4, 3, and 14 ankryrin (Ank) repeats in the TRPC subfamily, TRPV subfamily, and TRPA1, respectively. The NH₂ terminus of TRPMs is characterized by 4 stretches of residues, designated as the TRPM homology domain (MHD). The TRP domain (TRP-D) is present in the members of the TRPC and TRPM subfamilies. An enzyme domain is present in some of the channels, e.g., TRPM2 has an ADP-ribose pyrophosphatase, whereas TRPM6 and TRPM7 contain an atypical protein kinase. TRPP2 interacts with TRPP1, the 11-transmembrane protein, to form a channel complex.