We have outlined three important pieces of information above: first that the Q tunnel has additional Q binding sites (section 3) including sites closer to the E channel (sites 4/5, Fig. ), second that Q bound at a site near the E channel connects to the latter via a well-defined hydrated path (section 3, Fig. ), and third that the Q tunnel also connects to the N medium via additional cavities found in structures and simulations (section 4, Figs. and). This allowed us to stitch together a proton pumping model of complex I (16) (see section 2). This model, of which the foundations can be found in the proton pumping mechanism of complex IV (1), takes into account all three of the data described above and considers anionic SQ and QH -as two central species that drives proton pumping.