Structure based amino acid sequence alignment of the catalytic cores of the pART gene family. A) The alignment is restricted to those regions corresponding to the conserved secondary structure units of PARP-1 and DT as highlighted in Figure 1. The H Y E motif is marked by asterisks and is highlighted in red. Black numbers indicate amino acid residues from the N- and C-terminal ends of the protein and within the loops connecting the structure units shown. For proteins with known 3D structures the pdb accession number is given and the residues corresponding to respective secondary structure units are underlined. 1tox = diphtheria toxin; 1aer = pseudomonas exotoxin A, 3pax = chicken PARP-1 (pART1), 1gs0 = mouse PARP-2 (pART2). Human and mouse pARTs are indicated by colored numbers. The sequence of the putative pART from Chilo iridescent virus is also shown for comparison (ci). B) Pairwise percentage sequence identities were calculated for the 66 amino acid residues shown in A), which correspond to the conserved core secondary structure units in Figure 1.