Proton NMR study of the influence on iron oxidation/ligation/spin state on the heme orientational preference in myoglobin

Characterization of Heme Orientational Disorder in a Myoglobin Reconstituted with a Trifluoromethyl-Group-Substituted Heme Cofactor

“…The heme orientational disorder of a b -type hemoprotein has been investigated through studies of the reconstitution of wild-type and genetic variant proteins with not only native heme, but also a variety of chemically modified ones. − NMR − ,− ,− ,− ,,,− , is generally used to characterize the heme orientational disorder, and circular dichroism and resonance Raman , spectroscopies have been reported to be useful for identifying the presence of the reversed heme orientation. As functional consequences of the heme orientational disorder, pH-dependent oxygen (O 2 ) affinity, i.e., Bohr effect, in monomeric insect Chironomus thummi thummi hemoglobins ( CTT Hbs), reduction potential of bovine cytochrome b 5 (cyt b 5 ), cooperative O 2 binding properties of human adult Hb, and O 2 affinity of rainbow trout Mb have been reported to be affected by the heme orientation.…”

“…The heme orientational disorder demonstrated that the molecular recognition upon insertion of the heme into the Mb heme pocket is not as strict as that for the formation of usual enzyme–substrate complexes . Furthermore, broad molecular recognition of the Mb heme pocket is clearly reflected in its capacity to accommodate a variety of guest molecules ranging from chemically modified heme complexes − ,,,− and analogues ,− to metal complexes with salophen ligands . Characterization of the molecular recognition of the Mb heme pocket is a problem of particular importance for elucidating the heme-protein interaction and thus crucial for functional control of the protein.…”