Homology modeling of the NUDT9-H domain from the human TRPM2 channel protein. (A) Schematic diagram showing the membrane topology of the TRPM2 channel proteins. Important domains are labeled in the figure. (B) Sequence alignments of the human NUDT9 and NUDT9-H domain. Red shading with purple border denotes identical residues, and white shading with purple border denotes similarities. (C) Ribbon presentation of the homology models of the NUDT9-H domain based on the human NUDT9 structure. The α-helices, β-sheets, and loops are labeled in red, cyan, and gray, respectively.