Fig. 2.

Ca²⁺, Tb³⁺ and Ho³⁺ ions inhibit the activity of the purified PM H⁺-ATPase independently of an intact autoinhibitory domain. ATP hydrolytic activity of the C-terminal truncated PM H⁺-ATPase (aha2Δ73) and the full-length PM H⁺-ATPase (AHA2) was measured with varying concentrations of: (A) Tb³⁺ ions, (B) Ho³⁺ ions, and (C) Ca²⁺ ions. The activity without the addition of ions were set to 100% in A, B, and C. ▪, aha2Δ73; ◊, AHA2. All experiments are represented as ± S.D.