Conversion of Hemoprotein Function by Chemical Modification.

Myoglobin, one of the hemoproteins, is a well-known protein which has a protoporphyrin IX iron complex via noncovalent interaction. Therefore, a myoglobin with a synthetic heme is readily available by reconstitutional method. We have recently prepared various heme moieties having modified heme-propionates and incorporated them into an apomyoglobin to obtain a reconstituted protein. The myoglobin has an artificially created interface which acts as the binding domain to form a protein-protein or protein-small substrate complex. As a result, the myoglobin is converted to an electron transfer protein or oxidase. Thus, the present method gives a unique function to the myoglobin surface. Furthermore, it is found that the modification of heme framework is also an attractive approach to improving physiological function of hemoproteins. For example, an iron porphycene as a structural isomer of the heme is a good prosthetic group for the myoglobin to show a high dioxygen affinity. The net results propose that the reconstitutional method of hemo-proteins will serve as a new way in creating a functionalized protein by organic synthetic method.