Determining the Structure and Location of the ATP Synthase in the Membranes of Rat’s Heart Mitochondria Using Cryoelectron Tomography

The structure of the ATP synthase of rat’s heart mitochondria is determined by cryoelectron tomography (cryo-ET). The experiments are carried out on fragments of mitochondrial membranes without the additional purification of samples, which allows us to study the mitochondrial enzymes in the natural phospholipid and protein environment. The use of subtomographic averaging yields the structure of the ATP synthase with a resolution of about 13 A, as well as the structure of a stable dimer of ATP synthases with a resolution of about 15 A. The classification of the obtained subtomograms containing ATP synthases showed that this enzyme is always located on the bends of the phospholipid bilayer, while there are two groups of ATP synthase dimers that differ in the membrane curvature in the regions of their localization. On the obtained three-dimensional structures, both extramembrane and intramembrane synthase subunits are quite clearly distinguishable, which indicates the prospects of the chosen methodological approach for studying polyenzyme systems in the natural environment.