Fig. 1. The ε subunit of E. coli F₁F_o ATP synthase.

a Schematic of E. coli F₁F_o ATP synthase with subunits colored and labeled. The ε subunit is shown in green in the inhibited up conformation. b Crystal structure of the ε subunit in the up conformation (PDB:3oaa¹⁶), with α, β, and γ subunits removed for clarity. c Crystal structure of the isolated ε subunit in the down conformation (PDB:1aqt²⁰).