Superposition of a RNAP-δ-HelD complex and E. coli EC.

Color coding: α1, yellow; α2, gray; β, black; β’, white; ε, lime green; δ, slate blue; Zn, dirty violet; HelD, red; EC nucleic acids, orange; EC Mg, AS loop and flanking regions, cyan.

Catalytic Asp triads are shown as sticks.