Epsilon A two-domain protein: The N-terminus has 10 β-strands in two sheets that make a "sandwich". The C-terminus has two helices arranged in a "hairpin". Arg 85 from the 10th β-strand, is in blue, spacefilling. It ion-pairs with Glu 60, from the 7th and adjacent β-strand, shown in magenta, spacefilling. Glu 60 also packs against Phe 16, in the 2nd β-strand, from the other sheet. Uhlin U, Cox GB, Guss JM. Crystal structure of the epsilon subunit of the proton-translocating ATP synthase from Escherichia coli. Structure. 1997 Sep 15;5(9):1219-30.(PubMed) 1aqt (PDB)

Co-crystal of epsilon with the globular domain of gamma The β-sandwich domain of epsilon is unchanged, but the α-helices have moved. Arg 85 of epsilon, shown again in blue, spacefillling, is now in an ion-pair with Glu 225, shown in red spacefilling. Glu 60 and Phe 16 are unchanged. Rodgers AJ, Wilce MC. Structure of the gamma-epsilon complex of ATP synthase. Nat Struct Biol. 2000 Nov;7(11):1051-4. (PubMed) 1fs0 (PDB)