Fig. 3. DarB interacts with Rel_Bs via the SYNTH domain.

(A) Rel_Bs:DarB primary interaction interface involving α13 and β3 from Rel_Bs and α1, α2, β1, and β2 from DarB. (B) Rel_Bs:DarB secondary interaction interface formed between the α13/β3 connecting loop from Rel_Bs adjacent to the SYNTH active site and the α2/α3 loop of DarB. (C) Superposition of Rel_Bs^NTD in the SYNTH-primed state (colored as per Fig. 2C) onto Rel_Bs^NTD in the resting state shown in light gray (PDB ID 6YXA). The 20° movement of the HD domain away from the SYNTH domain observed in Rel_Bs^NTD in complex with DarB compared with the resting Rel_Bs (PDB ID 6YXA) is indicated with a black arrow.