Schematic representation of domains found in PARP proteins. Proteins are arranged by clade as defined in Figure 1 and in the text (indicated on the left). The protein name is given on the right, with species in parenthesis. Numbers indicate amino acids. Protein domains are illustrated by coloured boxes and were defined according to Pfam 23.0. Although each protein is represented in scale, the proteins are not in scale between each other. vWA, von Willebrand factor type A; VIT, vault inter-alpha-trypsin domain; Ankyrin, ankyrin repeats; UBCc, ubiquitin conjugating enzyme catalytic domain; PfamB_2311, domain of unknown function found in Clade 6 PARPs; UIM, ubiquitin interaction motif; PARP catalytic, catalytic domain of PARPs, PARP Zn2+, DNA binding zinc finger; Macro, macro domain; WWE, WWE domain; SAM, sterile alpha domain; PRD, PARP regulatory domain; PADR1, domain of unknown function found in PARPs; BRCT, BRCA-1 C terminus domain; CCHH Zn2+, DNA binding zinc finger; RRM1, RNA-binding motif; FPE, Fungal PARP E2-like domain; WGR, domain defined by conserved Trp, Gly, and Arg residues; U-box, modified ring finger found in E3 ubiquitin ligases; SAP, DNA binding domain. Human, Homo sapiens; Dictyostelium, Dictyostelium discoideum; Arabidopsis, Arabidopsis thaliana; Magnaporthe, Magnaporthe grisea; Physcomitrella, Physcomitrella patens.