and also the mirror image of complex I from the water channels paper
and highlight the important bits, we get this
which can be rearranged to give this
which animates as a gif to show how the change in the doohickey, induced by electron transfer to CoQ, is associated with the protonation (yellow cross proton) of an amino acid in the NuoH/Nqo8 water channel:
and then we can add in the orange-crossmarked pumped protons like this:
.gif)
This story explains the simple translocation of the three protons through the three antiporter-like subunits but gives us no insight as to how the fourth proton might be translocated.
And trying to reverse engineer the doohickey-NuoH water channel seems like the best chance of guessing at what happened as an intermediate process between using a geothermal proton gradient and generating a metabolic proton gradient. Each step must be immediately beneficial to early LUCA.
Peter
