Fig. 3: Oxygen entry site and channel composition.

a Surface representation of CcO and its oxygen entry point located between the transmembrane helix (TMH) 1 and 3 in the hydrophobic transmembrane site. The illustrated map density is filtered to a contour level of 2. b Detailed composition of the oxygen-conducting channel based on their hydrophobicity. The illustrated map density is filtered to a contour level of 0.5. c Interior channel embedded in between six transmembrane helices and channel lining residues predicted by Mole 2.5. d Overlay of channel prediction and individually displayed lining residues with corresponding dioxygen densities. Dioxygen molecules are shown as purple sticks, the corresponding densities are highlighted by mesh volumes.