Arginine myoglobins

Fig. 25. Stereodrawings of the two conformations of arginine-45 of carbon monoxy-myoglobin from sperm whale, (a) Conformation I, which is comparable to the conformation normally observed in metmyoglobin from sperm whale, (b) Conformation 2, which is stabilized by an amino-aromatic interaction between arginine-45 and phenylalanine-43.

Redaelli C, Monzani E, Santagostini L et al (2002) Characterization and peroxidase activity of a myoglobin mutant containing a distal arginine. ChemBioChem 3 226-233... 

C(NH2)2+ unit of arginine, via the formation of hydroxylamine. It can be characterized by ESR spectroscopy using deoxy-myoglobin or -haemoglobin with which it reacts to give nitrosyl derivatives having well-defined spectra. Its chief biological role seems to be as a vasorelaxant (Moncada et al., 1988). 

NH Resonances from tryptophan, arginine and histidine have been observed for myoglobin [36] in the range of 10-15 ppm. Deoxyhaemoglo-bin, dissolved in H2O at pH 7.4, has a resonance at 14 ppm which disappears upon ligation of the protein [37]. It has been used [38] as an indicator of quaternary structure as it is unaffected by unpaired iron-spin or porphyrin ring-current. 

The answer is d. (Murray, pp 48-62. Scrivei pp 3-45. Sack, pp 1-3. Wilson, pp 101—120.) The structure of myoglobin is illustrative of most water-soluble proteins. Globular proteins tend to fold into compact configurations with nonpolar cores. The interior of myoglobin is composed almost exclusively of nonpolar, hydrophobic amino acids like valine, leucine, phenylalanine, and methionine. In contrast, polar hydrophilic residues such as arginine, aspartic acid, glutamic acid, and lysine are found mostly on the surface of the water-soluble protein. 

Electrostatic Interaction. Electron transfers in supramolecular systems with electrostatic interaction have also been reported. A rapid electron transfer within a cofacial heteroporphyrin dim was reported [621]. A cofacial ionic interaction between porphyrin and anthraquinone sulfonate was observed to be controlled by sugar hydroxylate [620]. As a model system of cytochrome c-peroxidase interaction [608,609], a reconstituted myoglobin with Zn porphyrin was associated with methylviologen through electrostatic interaction and the forward electron transfer was observed to be more favored than the back electron transfer [610] (Fig. 56). In a salt-bridged supramolecules having Zn amidinium porphyrin and aromatic carboxylate as a model of arginine-aspartate interaction [606], the electron transfer was considerably more decreased than expected [607]. 

---