Fig. 4: Inter-tetramer interactions are required for DRT1 activity.
From: Semirandom DNA adducts regulate a filamentous defense-associated reverse transcriptase
a, The DRT1 octamer, with domain-swapped C termini shown in the inset. The sequence logo of the C-terminal residues is generated from alignment of 174 DRT1 sequences. b, Orientation of protomers with domain swapping interactions. A prime symbol (′) indicates a protomer from a different tetramer stack. c, Interactions between proximal residues to the nitrilase active site (light pink) and the swapped C terminus of the adjacent protomer (purple). Nitrilase catalytic tetrad residues are labeled in yellow. d, DRT1 nitrilase domain (light pink) superimposed with the dimeric unit of closed-lid conformation nitrilase from Rhodococcus sp. V51B (PDB 8UXU) (blue) and its benzaldehyde substrate (magenta). The domain-swapped C terminus of a DRT1 protomer is shown in purple, and the nitrilase active-site catalytic tetrad is shown as sticks. The dashed circle shows the lid region. e, Superposition of the DRT1 nitrilase active-site catalytic tetrad (light pink) with that of a nitrilase filament from Rhodococcus sp. V51B (PDB 8UXU) (blue). f, Structure-guided mutations suggested to disrupt DRT1 activity, with mutation locations shown as purple spheres in the structures, and a heatmap of phage plaquing assay relative to DRT1wt. Darker shades indicate loss of immunity. The heatmap represents the average of n = 3 independent experiments.
