Haemoglobin ribbon representation

S Fig. 28.7 (a) The structure of haemoglobin shown in a ribbon representation. The four subunits, each containing a haem unit, are shown in different colours, (b) The structure of the haem unit in its rest state. The Fe(II) centre is coordinated by a protoporph5Tin IX ligand and a histidine residue the non-terminated stick represents the connection to the protein backbone. Hydrogen atoms are omitted for clarity. Colour code Fe, green C, grey N, blue O, red. 

Fig. 3 d, e. Crystal stuctures of human haemoglobin in the oxy [83S] and deoxy [84F] states, protein data bank entries IHHO and 2HHB. The orientation is as in (a). a-Helices are drawn as wound ribbons and are colored pink in the a subunits and red in the (3 subunits. The haem groups are shown in ball-Stick representation. The color code used for atoms is black for carbon, blue for nitrogen, red for oxygen and grey for iron. 

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