Your Rotary Engines Are Arranged in Factories
As if ATP synthase was not amazing enough, a team of scientists in Germany now tells us they are arranged in rows with other equipment to optimize performance. From electron micrographs of intact mitochondria, they were able to detect the rotary engines of ATP synthase and other parts of the respiratory chain. Their diagram in an open-source paper in PNAS looks for all the world like a factory.
CEH has reported on ATP synthase many times (for concise explanation with animation, see CMI). Your body, and every other living thing on earth, depends on a steady supply of the ATP “energy pellets” they synthesize. The two-part rotary engines rely on a constant flow of protons (proton motive force, or pmf). These protons are produced by other engines, Complex I (NADH dehydrogenase; for structure of this piston engine, see 07/06/2010), Complex III (cytochrome c reductase), and Complex IV (cytochrome c oxidase), through a series of mechanical and chemical reactions. The protons enter ATP synthase through its bottom structure, called F0, which is embedded in the mitochondrial membrane, causing it to rotate (the authors said it “works like a proton-driven turbine”). A stator and central stalk transfer the energy to the top part, F1, where three catalytic centers, arranged like orange slices, take in ADP and phosphate to create ATP – molecules with stored energy that travel throughout the cell to power almost everything.
Each of these molecular machines are wonders of design efficiency in themselves. The new paper by Davies et al. augments that wonder by showing how they are all arranged for maximum performance.1 In order to save words, we are attaching their diagram (Figure 5) from the open-source paper; readers are encouraged to go to the source provided for caption and details.1 The proton-pumping machines (green) are arranged along folds of the cristae (blue) so that the protons don’t wander away from the ATP synthase machines (yellow). Since Complexes I, III, and IV act as proton “sources” and ATP synthase as proton “sinks”, a flow is set up toward the tight folds where the ATP synthase (yellow) are located.
In addition, the ATP synthase engines are so arranged in pairs (dimers), their F0 parts almost touching, their F1 parts separated, by angles ranging from 40° to 70° depending on the species. These dimers are then arranged in long rows like one might see in a hydroelectric plant. In this way, the flow of protons is channeled exactly where it is needed for optimal performance of the turbines. Concerning this “striking arrangement,” the authors said, “We propose that the supramolecular organization of respiratory chain complexes as proton sources and ATP synthase rows as proton sinks in the mitochondrial cristae ensures optimal conditions for efficient ATP synthesis.”
The authors had virtually nothing to say about how this might have evolved, noting only that the structure is “conserved during evolution” in every sample they examined (3 species of fungi including yeast, potato, and mammal). What this means is a lack of evolution over nearly two billion years, in the standard evolutionary timeline. Furthermore, it is apparent that evolutionary theory contributed little or nothing to their investigation. It was really a study of how these structures are optimized for function: “The mutual arrangement of electron transfer complexes as proton sources and ATP synthase complexes as proton sinks in the membrane is therefore of fundamental interest and importance for understanding mitochondrial energy conversion.” They used the word optimal three times in the paper.
1. Davies et al., “Macromolecular organization of ATP synthase and complex I in whole mitochondria,” Proceedings of the National Academy of Sciences, published online before print August 11, 2011, doi: 10.1073/pnas.1103621108.
We have to just keep piling it on till people get it and vote Darwin out of office as Science Czar. In terms of understanding designs in nature like this, are you better off than you were 150 years ago?