Partial multiple sequence alignment of selected eukaryotic and prokaryotic H-NOB proteins. Numbering on top corresponds to the H-NOB domain of T. tengcongensis. Residues conserved among all H-NOB proteins and important for heme binding are highlighted in red. The Tyr-140 residue, which is essential for the stabilisation of O2 binding in T. tengcongensis is highlighted is green. The names of the two cyanobacterial sequences present are hightlighted in red.