Figure 1

Structural classes and evolutionary relationships of RCD1 and RCD1-like proteins. (A) Schematic diagram depicting the protein structure of A. thaliana RCD1/SRO protein family members representing the two structural classes, type A (AtRCD1) and B (AtSRO2). RCD1 and all SROs possess a poly(ADP-ribose) polymerase (PARP) catalytic region (PS51059) and a C-terminal RST (RCD1-SRO-TAF4; PF12174) domain. Additionally, the presence (type A) or absence (type B) of a WWE domain (PS50918) differentiates between the two structural classes. Human HsPARP11 exhibits similar domain composition to the Arabidopsis SROs containing a WWE domain and the PARP domain. It is representative of the five human WWE-PARPs although the remaining four have additional conserved domains. (B) A. thaliana and A. lyrata SROs clustered in three groups in an unrooted Neighbour-joining tree. AtRCD1 and AtSRO1 and the A. lyrata orthologs AlSRO1a and AlSRO1b formed group I, which structurally belongs to type A. AtSRO2 and AtSRO3 and the A. lyrata orthologs AlSRO2a and AlSRO2b formed group IIa. AtSRO4 and AtSRO5 and the A. lyrata orthologs AlSRO2c and AlSRO2d form group IIb. All members of group II belong to structural type B. (C) Neighbour-joining tree of the A. thaliana and A. lyrata SROs rooted the A. thaliana PARPs (AtPARP1, 2 and 3). The SRO proteins clustered together and form a monophyletic group while AtPARP1, 2 and 3 clustered together to form a single outgroup for the SRO protein family.