Fig. 1. Crystal structure of the A. thaliana OTP86 DYW domain.

a, Superimposition of OTP86^DYW (marine) with E. coli cytidine deaminase (EcCD^Z, cyan) bound to the inhibitor zebularine (not shown) (PDB-ID: 1CTU; ref. ³²). The consensus deaminase zinc ions are shown as green (OTP86^DYW, Zn1) and light-green (EcCD^Z, Zn) spheres, a zinc ion partially coordinated by the DYW motif is shown in yellow (Zn2). b, The OTP86^DYW structure defines a paradigmatic organization for DYW domains. The cytidine deaminase domain (slate) coordinates a zinc ion (Zn1, green) three-fold with H892, C920 and C923, the fourth position is occupied by a water molecule (W, white sphere). The deaminase domain is interrupted by a gating domain (orange) and terminates with a DYW motif (red), partially coordinating a second zinc ion (Zn2, yellow). c, A close-up view on the cytidine deaminase active site, with catalytically relevant residues shown as sticks. d, A close-up view of the DYW motif and the flanking β-strand 7 as well as α-helix 3. e, Electrostatic surface potentials as indicated by the colour scale bar (bottom), obtained by APBS version 1.5 and plotted on the surface of OTP86^DYW. Residues involved in zinc coordination are shown as sticks; zinc atoms are as in b. Rotation symbols indicate the views relative to b. Interacting residues are shown as sticks and coloured by atom type. Blue, nitrogen; red, oxygen; yellow, sulfur; carbons take the colour of the respective molecule. Dashed lines represent hydrogen bonds, whereas thick grey dashed lines indicate zinc coordination. Dashed lines in the ribbon plots represent residues 842-844 not clearly defined by electron density.