ATP synthase: from single molecule to human bioenergetics

ATP synthase (FoF1) consists of an ATP-driven motor (F1) and a H+-driven motor (Fo), which rotate in opposite directions. FoF1 reconstituted into a lipid membrane is capable of ATP synthesis driven by H+ flux. As the basic structures of F1 (α3β3γδε) and Fo (ab2c10) are ubiquitous, stable thermophilic FoF1 (TFoF1) has been used to elucidate molecular mechanisms, while human F1Fo (HF1Fo) has been used to study biomedical significance. Among F1s, only thermophilic F1 (TF1) can be analyzed simultaneously by reconstitution, crystallography, mutagenesis and nanotechnology for torque-driven ATP synthesis using elastic coupling mechanisms. In contrast to the single operon of TFoF1, HFoF1 is encoded by both nuclear DNA with introns and mitochondrial DNA. The regulatory mechanism, tissue specificity and physiopathology of HFoF1 were elucidated by proteomics, RNA interference, cytoplasts and transgenic mice. The ATP synthesized daily by HFoF1 is in the order of tens of kilograms, and is primarily controlled by the brain in response to fluctuations in activity

Rows of ATP Synthase Dimers in Native Mitochondrial Inner Membranes

The ATP synthase is a nanometric rotary machine that uses a transmembrane electrochemical gradient to form ATP. The structures of most components of the ATP synthase are known, and their organization has been elucidated. However, the supramolecular assembly of ATP synthases in biological membranes remains unknown. Here we show with submolecular resolution the organization of ATP synthases in the yeast mitochondrial inner membranes. The atomic force microscopy images we have obtained show how these molecules form dimers with characteristic 15 nm distance between the axes of their rotors through stereospecific interactions of the membrane embedded portions of their stators. A different interaction surface is responsible for the formation of rows of dimers. Such an organization elucidates the role of the ATP synthase in mitochondrial morphology. Some dimers have a different morphology with 10 nm stalk-to-stalk distance, in line with ATP synthases that are accessible to IF1 inhibition. Rotation torque compensation within ATP synthase dimers stabilizes the ATP synthase structure, in particular the stator-rotor interaction

Jumping Mode Atomic Force Microscopy on Grana Membranes from Spinach

The thylakoid membrane system is a complex membrane system that organizes and reorganizes itself to provide plants optimal chemical energy from sunlight under different and varying environmental conditions. Grana membranes are part of this system and contain the light-driven water-splitting enzyme Photosystem II (PSII) and light-harvesting antenna complexes. Here, we present a direct visualization of PSII complexes within grana membranes from spinach. By means of jumping mode atomic force microscopy in liquid, minimal forces were applied between the scanning tip and membrane or protein, allowing complexes to be imaged with high detail. We observed four different packing arrangements of PSII complexes, which occur primarily as dimers: co-linear crystalline rows, nanometric domains of straight or skewed rows, and disordered domains. Upon storing surface-adhered membranes at low temperature prior to imaging, large-scale reorganizations of supercomplexes between PSII and light-harvesting complex II could be induced. The highest resolution images show the existence of membrane domains without obvious topography extending beyond supercomplexes. These observations illustrate the possibility for diffusion of proteins and smaller molecules within these densely packed membranes