Lysine myoglobins

The most common carrier proteins in use today are keyhole limpet hemocyanin (KLH MW 4.5 X 105 to 1.3 X 107), BSA (MW 67,000), aminoethylated (or cationized) BSA (cBSA), thyroglobulin (MW 660,000), ovalbumin (OVA MW 43,000), and various toxoid proteins, including tetanus toxoid and diphtheria toxoid. Other proteins occasionally used include myoglobin, rabbit serum albumin, immunoglobulin molecules (particularly IgG) from bovine or mouse sera, tuberculin purified protein derivative, and synthetic polypeptides such as poly-L-lysine and poly-L-glutamic acid. 

One simple case of disordered structure involves many of the long charged side chains exposed to solvent, particularly lysines. For example, 16 of the 19 lysines in myoglobin are listed as uncertain past C8 and 5 of them for all atoms past C/J (Watson, 1969) for ribonuclease S Wyckoff et al. (1970) report 6 of the 10 lysine side chains in zero electron density in trypsin the ends of 9 of the 13 lysines refined to the maximum allowed temperature factor of 40 (R. Stroud and J. Chambers, personal communication) and in rubredoxin refined at 1.2 A resolution the average temperature factor for the last 4 atoms in the side chain is 9.2 for one of the four lysines versus 43.6, 74.4, and 79.3 for the others. Figure 57 shows the refined electron density for the well-ordered lysine and for the best of the disordered ones in ru-... 

These techniques have been used successfully in the micro-Zdman degradation of the enzyme mouse sarcoma dihydrofolate reductase to obtain the amino acid sequence of the first 25 amino acids 455). Similarly, RPC has been used in coqjunction with the automated Edman technique for sequencing 32 residues of myoglobin 456). Methionine and its oxidation products, methionine sulfoxide and methionine sulfone, in methionine fortified foods have been analyzed as their dansyl derivatives 457). Lysine has been determined as its dansyl derivative in a study in which the stability of lysine in fortified wheat flour was evaluated (458). 

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. 

Normalized Specific Activities Among Native Proteins. Figure 9 shows a comparison of tritium distributions for native proteins irradiated to about 6 Mrads (except for myoglobin which was irradiated to 23 Mrads). Each bar represents the average normalized specific activity of five separate labeling experiments for ribonuclease and of two for each of the other proteins. The tritium distributions have many similarities. The activities of proline and methionine are generally high. Lysine and histidine are heavily labeled in most proteins, while threonine and serine... 

Each protein has, within this general pattern, its own characteristic radical distribution. In ribonuclease, lysine exhibits a much higher activity than do the remaining amino acids. Lysine and methionine are the most heavily labeled residues in lysozyme. In myoglobin, histidine has the highest activity. Methionine is the most heavily labeled amino acid in chymotrypsinogen, as is proline in insulin. Despite the similarities, therefore, each native protein exhibits a characteristic tritium distribution. 

Susi et al. (1967) have observed spectra of poly-L-lysine, poly-L-glutamic acid, )S-lactoglobulin, myoglobin, and a -casein in the region of absorption of the amide I band in HjO and DjO solutions, and in the solid state. Their results indicated that characteristic frequencies exhibited by specific conformations of the synthetic polypeptides studied are not transferable to corresponding conformations of globular proteins. 

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