The haem distal site of MaPgb*(III)-cyanide.
Residues lining the haem distal pocket are indicated and shown in stick representation (yellow). Superimposition of MaPgb*(III)-cyanide to (A) ligand-free MaPgb*(III) (magenta), and (B) MaPgb*(II)-O2 (cyan). The proximal His(120)F8 residue is also shown. Amino acid residues have been labeled using their three-letter codes, the sequence numbering (in parentheses), and the topological site they occupy within the globin fold. In panel (A) the haem distal cavity entrance sites of tunnel 1 and tunnel 2 are indicated by arrows. Both panels are shown from a side and a top view. Rotation of the Phe(93)E11 side chain upon ligand binding is indicated in each top view panel. H-bonds to the haem-Fe(III)-bound cyanide are indicated by dashed lines.