Fig. 3.

Purification and EM of Stv1-V_O. (A) Coomassie-stained SDS/PAGE gel shows a mixture of intact V-ATPase and V_O complexes when purified by a 3×FLAG tag on Stv1p at OD₆₆₀ = 0.5, isolated V_O complexes when purified by a 3×FLAG tag on Stv1p at OD₆₆₀ = 12, and intact V-ATPase when purified by a 3×FLAG tag on Vma1p (subunit A) at OD₆₆₀ = 6. (B) Atomic model of the Stv1-V_O complex. Essential proton-carrying glutamate residues on the c-ring are shown in red. R795 and R862 from Stv1p are in contact with the essential glutamate residue E108 on subunit c″. (Scale bar, 25 Å.)