Heme protein structure and ligand binding

Abstract

Binding of carbon monoxide to a variety of heme proteins is a multistep process and can be described by a sequence of activation barriers. In the separated alpha and beta chains of hemoglobin three barriers are found which are sensitive to the structural differences between the two chains. The barriers in the beta chain change when two cysteine amino acids are modified with a mercury compound. Three processes are also observed in CO binding to cytochrome P4S0 and rates depend strongly upon the presence of the enzyme's substrate, camphor. Comparisons among these and other heme proteins and compounds show that protein structure can influence any of the activation barriers.