Extended Data Fig. 6: Comparison of CD-NTase and E2 homologs.

a, Sequence logos for CD-NTase (cGAS) from type II CBASSs. Left and right show sequence logos for the C-terminal 10 residues of CD-NTase from E1E2/JAB-CBASSs and E2-CBASSs, respectively. Data are depicted as bits and signified by the height of each residue. Different colors indicate the chemical properties of amino acids. See also Supplementary Fig. 1, 3. b, Sequence alignment of E2 homologs from E2-CBASSs and E1E2/JAB-CBASSs show that they share low homology. The two crucial histidine residues (marked by red triangles) are conservative in E2 from E2-CBASSs but not E1E2/JAB-CBASSs. See also Supplementary Fig. 2, 4, 5. c, Sequence logos for the active site sequences of Cap2 (E2) from E2-CBASSs. Top left and right show 20 amino acids upstream and downstream of the active site cysteine, and 5 amino acids upstream and downstream of the residues corresponding to H152, respectively. The positions corresponding to H87, C101, and H152 are marked by red triangles. Bottom, Sequence logo for the active site sequences of E2 domain of Cap2 (E1E2) from E1E2/JAB-CBASSs. 20 amino acids upstream and downstream of the active site cysteine are shown. The active site cysteine is marked by a red triangle. Data are depicted as bits and signified by the height of each residue. Different colors indicate the chemical properties of different amino acids. See also Supplementary Figs. 2, 4. d, Superimposed structures of E2 (orange) and human E2 (gray, PDB ID 4AUQ) show that no similar catalytic site is found in human E2.