FIGURE 5.

Front view of Trp-58(E7) α subunit in hybrid deoxyHb. Different conformers of α His-45(CE3) are observed in the α₁ and α₂ subunits of deoxygenated α(Trp-58(E7))β(WT) tetramers (Protein Data Bank code 3NMM). The stick models of the key amino acids are colored as follows: white, carbon; blue, nitrogen; red, oxygen. The atoms of the other amino acids are represented as space-filling yellow spheres. The orange sphere represents the heme iron. The blue dotted line in the α₂ subunit represents a hydrogen bond between His-45(CE3) and the heme 6-propionate with an interatomic distance of 3.0 Å.