Structural similarities between the N-terminal domains of AAV2-Rep and R388-TrwC.

(A) Topology diagram of the OBD domain of Rep (left) and relaxase domain of TrwC (right). The portion of the structure that forms the core active site typical of HUH endonucleases, consisting of five anti-parallel β-sheets and one α-helix and containing the active site tyrosine (helix E in AAV-Rep and helix A in R388-TrwC), is highlighted in red and blue, respectively. Helices with some degree of overlap are shown with their name (C and D in AAV-Rep, E and G in R388-TrwC). (B) Ribbon diagrams shown in the same orientation as in (A), with the active site tyrosine highlighted in yellow and the consensus HUH motif in green. TrwC has 2 active tyrosines, Tyr18 and Tyr26, but only Tyr18 is mapped in the TrwC structure. (C) Structural alignment of the HUH domains of Rep (red) and TrwC (blue) showing a high degree of similarity between the active sites of the two proteins, while no similarities are noted in the rest of the protein structure (shown in orange and violet, respectively).