Figure 5.

Model for reassembly of autoinhibited V₁ and V_o. A–C, our in vitro experiments have shown that although WT H containing V₁ does not readily bind V_oND (A), V₁H_chim spontaneously associates with V_oND (B) to form a structurally and functionally coupled V-ATPase, albeit at a slow rate. C, in vivo, however, V₁ exists in the autoinhibited conformation (A), and the rate of assembly with V_o is significantly faster (within 5 min). D–F, for in vivo (re)assembly, we propose that the following steps occur: step 1, recruitment of V₁ and subunit C to the vacuolar membrane (D); step 2, release of inhibitory MgADP (E); step 3, detachment of H_CT from its inhibitory position on V₁; and step 4, H_CT binding to a_NT (F). For further details, see text.