The OXPHOS System Today (IMAGE)
Caption
The figure shows a new view of the how we believe that this OXPHOS system is organized and work in the cell. Briefly, the five complexes are not independently moving within the membrane. On the contrary they can physically associate in different combinations called respiratory supercomplexes. These associations are dynamic and can be modify to optimize the extraction of energy from the high-energy electrons depending of the proportion of NADH+H+/FADH2 available or, in other words, depending of the proportion of sugar and fat consumed. The major associations observed are supercomplex containing complexes I, III and IV, also named respirasomes, supercomplexes containing complex I and III (SC I+III) or supercomplexes containing complex III and IV (SC III+IV). Complex III and complex IV can be observed also in free form but complex I is almost always observed associated with other complexes. The primary consequence of this new view is that if SCs I+III or I+III+IV will only receive electrons from NADH. On the other hand, SC III+IV or free CIII will only receive electrons from FADH2. Finally free CIV will be able to receive electrons either from NADH, through SC I+III or from FADH2, trough free CIII. All this imply that the fundamental system in the cells to optimize the extraction of energy from the food is more versatile that it was thought and that can be fine-tuned by this structural plasticity to efficiently perform its role in different food regime, specialized cell types, etc.
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CNIC
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