Proton-coupled structural changes upon binding of carbon monoxide to cytochrome cd(sub.1): a combined flash photolysis and X-ray crystallography study

Dynamic events after flash photolysis of carbon monoxide (CO) from reduced cytochrome d(sub.1) nitrate reductase (NiR) from Paracoccus pantotrophus (formerly Thiophaera pantotropha) have been studied. CO binds to the iron of the d(sub.1) heme in the active site and the ligation of the c heme is not changed in the complex. The proton-coupled structural changes associated with ligand binding likely affect the redox potential of heme d(sub.1) and may regulate the internal electron transfer from heme c to heme d(sub.1).