Significance F-ATP synthase is a fundamental enzyme supplying adenosine triphosphate (ATP), spreading across all kingdoms of life. Despite remarkable conservation of its basic structure and function, biophysical studies have revealed discrete differences in the rotary mechanisms of bacterial and eukaryotic F ₁ -ATPases (the catalytic portions of the enzymes). Here, we analyzed the rotational dynamics of Paracoccus denitrificans F ₁ (PdF ₁ ), a bacterial F ₁ -ATPase that exhibits high homology with the core functional subunits of its mitochondrial counterpart. Notably, PdF ₁ possesses a simplified chemomechanical scheme different from that of all other F ₁ -ATPases. Our results reveal an unexpected diversity in the chemomechanical coupling cycle of the F ₁ -ATPase machinery and show that features such as homology or phylogenetic relationship cannot uniquely define the rotary scheme pattern.