VPA1380 is related to the IP6-activated cysteine protease domain of MARTX and CGT toxins. Left Panel: A ribbon representation of the Vibrio cholerae MARTX cysteine protease domain (PDB 3fxy) depicts the region of the structure that confidently aligns to VPA1380 (colored slate, with unaligned region in white). The aligned region encompasses the Cys-His active site (black spheres), and a majority of the IP6 (cyan stick) binding site (magenta and pink). Right Panel: A zoom of the IP6 binding site highlights MARTX residues that form hydrogen-bonds to IP6 and map to conserved VPA1380 positions (magenta sticks, labeled in italics according to VPA1380 residues). Several MARTX residues that form the IP6 binding pocket were either mapped to the unaligned N-terminus or were not mutated (pink sticks).