Myoglobin heme modification

Myriad metalloproteins bind iron-protoporphyrin IX, known as heme (Fig. 15). Heme protein properties are determined by a variety of factors within the inner coordination sphere and without. These include chemical modifications to the porphyrin macrocycle, different axial ligation, perturbations to conformation, and protein dynamics surrounding the cofactor. Because of the extensive proliferation of heme proteins, we will limit ourselves to a small subset. These will include the cytochromes c, myoglobins, heme oxygenases and peroxidases, and a heme-based chemical sensor. 

Several modifications of protoheme are indicated in Fig. 16-5. To determine which type of heme exists in a particular protein, it is customary to split off the heme by treatment with acetone and hydrochloric acid and to convert it by addition of pyridine to the pyridine hemochrome for spectral analysis. By this means, protoheme was shown to occur in hemoglobin, myoglobin, cytochromes of the b and P450 types, and catalases and many peroxidases. Cytochromes a and a3 contain heme a, while one of the terminal oxidase... 

In Ref. [279] the technique of protein modification was used to study the dependence of the rate of photoinduced electron tunneling on the distance between TZnP and Ru(III) sites in modified myoglobins. The modified proteins were prepared by substitution of zinc mesoporphyrin IX diacid for the heme in four various pentaammineruthenium (III) derivatives of sperm whale myoglobin (NH3)5Ru(His-48)Mb, (NH3)5Ru(His-12)Mb, (NH3)5Ru(His-116)Mb and (NH3)5Ru(His-81)Mb. Metal-to-metal distance between ZnP and (NH3)5Ru(His) ranges in this seria from 16.1-18.8 A for His-48 to 27.8-30,5 for His-12. The rate constant of electron tunneling decreases in this series in accordance with Eq. (1) with ve = 7.8 x 10s s 1 and ae = 2.2 A at T = 298 K. 

Hayashi T, Hisaeda Y (2002) New functionalization of myoglobin by chemical modification of heme-propionates. Acc Chem Res 35 35 13... 

Chemically modified myoglobin and residues with small-sized substituents not containing reactive groups. In contrast, electron-rich substituents disrupted the heme structure The modification rates were slower for [61]... 

New functionalization of myoglobin by chemical modification of heme-propion-ates 02ACR35. 

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