Figure 6. The structure of BaDF2 member single-strand DNA deaminase toxin A (SsdA) bears little resemblance to double-stranded DNA deaminase A (DddA) and reveals motifs differentiating toxins from RNA-targeting DYW proteins.
(A) Ribbon diagram depiction of the SsdAtox-SsdAI structure. (B,C) Secondary structure diagrams for SsdAtox and the core fold of deaminase superfamily proteins (Iyer et al., 2011). The SWG motif conserved in BaDTF2 toxins and the accompanying α-helical insertion (blue) are indicated in B. (D) Active site view of SsdAtox. Catalytic and zinc-coordinating residues, SGW motif and α-helical insertion (blue) are indicated. (E) Active site view of DddAtox indicating catalytic and zinc-coordinating residues. (F) Zoom-in view of the contact site between SsdAI and the active site of SsdAtox. (G) Conserved motifs identified in DYW and BaDTF2 proteins.