Fig. 2.

Schematic demonstration of how small conformational changes to the heme upon binding with CO leverage big changes to the catalytic domain and thus its substrate selectivity and catalytic activity. The transformation of the five-coordinated heme into a six-coordinated heme pulls the histidine imidazole side change toward the heme plane, thus causing conformational changes that can be transduced to larger conformational changes of the functional domain (catalytic domain in this case) of the hemoprotein.