Figure 4. Superimposition of X-ray structures 1UT0 and HE7Q mutant.

Representation of the backbone of HE7Q Cygb* mutant (gray ribbon) and Cygb* in the endogenous bis-histidyl hexacoordinated state (subunit A, orange ribbon). The rigid body movement of helix E is indicated by an arrow. The HE7Q Cygb* heme group is in red colour. For clarity, the CN⁻ ion (not coordinated to the heme iron) is omitted from the HE7Q Cygb* distal cavity (see Figure S2). Relevant residues are labelled.