The molecular structure of an axle-less F₁-ATPase

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• F1F0 ATP synthase is a rotary motor generating ATP via proton motive force.
• F1-ATPase hydrolyzes ATP through conformational changes involving the gamma rotor and beta subunits.
• Cooperativity in F1-ATPase is traditionally attributed to the gamma subunit's interactions with beta subunits.

Purpose of the Study:

• To investigate the structural and functional role of the gamma subunit in F1-ATPase.
• To elucidate the mechanism of ATP hydrolysis and binding in axle-less F1-ATPase.

Main Methods:

• Cryogenic electron microscopy (cryo-EM) was used to determine the structure of axle-less Bacillus sp. PS3 F1-ATPase.
• Analysis of conformational states and subunit interactions in the absence of the gamma axle.

Main Results:

• The axle-less F1-ATPase adopted an unexpected binding-dwell conformation.
• Lack of interaction between the axle-less gamma subunit and open beta subunits was observed.
• Single molecule studies showed reduced efficiency in axle-less F1 complexes.

Conclusions:

• The complete gamma subunit is crucial for coordinating efficient ATP binding in F1-ATPase.
• The gamma subunit's role extends beyond conferring cooperativity to actively coordinating substrate binding.
• Structural insights reveal a novel mechanism for regulating F1-ATPase activity.