Molecular Processes of Inhibition and Stimulation of ATP Synthase Caused by the Phytotoxin Tentoxin

Abstract

F 1 -ATPase is the smallest mechanical motor known. Tentoxin, a cyclic peptide produced by phytopathogenic fungi, inactivates the F 1 motor in sensitive plants at nanomolar to micromolar concentrations, whereas higher concentrations surpass the natural activity of the enzyme. Single molecule studies now have clarified the molecular steps involved in both processes. Inactivation delays the dwell time of a single step in the complete 360°turn and results in an asymmetric rotation of the central rotor subunit. In contrast, rotation in the stimulated F 1 particle is smooth and accompanied by strongly reduced ADP inhibition. Our study provides for the first time the direct observation of a noncompetitively inhibited state of the enzyme and directly visualizes the regulation of the molecular motor by an external natural compound. In addition, the ADP release step during catalysis was revealed by analysis of the single molecule rotation behavior. Hence, tentoxin is a sophisticated molecular tool to mark and control certain catalytic steps within the reaction pathway of the molecular F 1 motor.

Structure of the c14 Rotor Ring of the Proton Translocating Chloroplast ATP Synthase

“…Structure of the Chloroplast c 14 Ring-The final model of the chloroplast c ring rotor consists of 14 identical protomers that are symmetrically arranged around a central pore (Fig. 2).…”

When and how to kill a plant cell: Infection strategies of plant pathogenic fungi

“…The crystal structure of spinach chloroplast F1 complexed with tentoxin illustrated that the catalytic site on the ␣␤ 1 dimer is in a closed conformation (Groth, 2002). Detailed experimental analysis shed light on the mechanism of tentoxin action and demonstrated that a single molecule of the toxin affects ADP release in a non-competitive manner (Meiss et al, 2008).…”

Correlation between the conformational states of F 1 -ATPase as determined from its crystal structure and single-molecule rotation

“…However, the fact that the crystal structures identified so far are comparable with the reference structure implies that the crystallization of F 1 in the binding dwell state is very difficult. One possible way is to crystallize F 1 at low temperature (16) or F 1 inhibited by tentoxin (36), where it spends most of the catalytic turnover time pausing at the binding dwell angle.…”