Figure 4.

V‐ATPase conformational changes accompanying reversible disassembly. (A) Conformational changes in the auto‐inhibited ScV₁‐ATPase (5d80).71 Upon holo enzyme dissociation, the C‐terminus of subunit H (H_CT) is released from its binding site on a _NT (in V₁V_o) and rotates 150º to bind at the bottom of the A₃B₃ hexamer (in V₁). H_CT binds to the B subunit of the open catalytic site, thereby stabilizing inhibitory ADP in another site.71 The inhibitory loop is in spacefill and the α helix that binds a _NT in V₁V_o is in orange. (B) CryoEM model of holo ScV₁V_o 45 (3j9u). (C) Conformational changes in the V_o proton channel (5tj5)26. Upon release of V₁‐ATPase from the membrane, the N‐terminus of subunit a (a _NT) moves from its ternary interface with C_foot and EG2 to form a new binding interface with subunit d 26, 73, 88 and the c‐ring is positioned so that Glu108 of isoform c″ is in contact with the essential Arg735 in a _CT.