What structural configuration does the F1 domain of mitochondrial ATP synthase possess?

The F1 domain of mitochondrial ATP synthase is indeed structured as a hexamer of 3 αβ dimers. In this configuration, three pairs of α and β subunits come together to form a hexameric assembly. Each of the β subunits plays a critical role in ATP synthesis, as they are the sites where ATP is produced from ADP and inorganic phosphate during oxidative phosphorylation.

This hexameric arrangement is crucial for the function of ATP synthase, allowing the enzyme to harness the proton gradient across the inner mitochondrial membrane created by the electron transport chain. This gradient is what drives the rotation of the central stalk and facilitates the synthesis of ATP in the F1 domain. The specific arrangement of three αβ dimers allows for the cooperative nature of ATP synthesis, providing a highly efficient mechanism for energy conversion in cells.

In contrast to the other configurations provided in the choices, such as a tetramer or dimers with different stoichiometries, they do not accurately represent the known structural assembly of the F1 domain. Thus, the correct depiction of the F1 domain's structure is indeed a hexamer of three αβ dimers.