IUPRED profiles for Mbs (A) and GlbNs (B). (A) The Mb sequences of sperm whale (sw, solid line), human (hu, long dashes), horse (eq, long grey dashes), and pig (pig, short dashes) are shown. The arrow indicates the proximal histidine, and the horizontal bars span the helical regions of the holoproteins. (B) The GlbN sequences of Synechococcus sp. PCC 7002 (solid line), Synechocystis sp. PCC 6803 (short dashes), and Nostoc commune (long grey dashes) are shown. The horizontal bars span the helical regions as defined in the structure of Synechocystis sp. PCC 6803 GlbN (1MWB). Arrows indicate the axial histidines of Synechococcus sp. PCC 7002 and Synechocystis sp. PCC 6803 GlbN, located at positions 46 (distal) and 70 (proximal). Nostoc GlbN appears to use His70 as only axial ligand (Thorsteinsson et al., 1999).