Cystine hemoglobin

Val-Cys-Ser-Leu-Tyr-Gln-Leu-Glu-Asn-Tyr-Cys-Asn-COO-. When only the composition is known (i.e., the sequence is unknown), the amino acids are separated by commas and enclosed in parentheses, for example, (Ala,Cys2,Gly) means a peptide containing one Ala, two Cys, and one Gly in an unknown order. A "polypeptide chain" is, by convention, a continuous chain linked only by peptide bonds. A protein may have only one polypeptide chain and then the polypeptide and the protein are synonymous. In other cases, a protein may have more than one polypeptide chain, as does insulin. In such cases, the different peptide chains within a protein may be held together by noncovalent forces, as in the case of hemoglobin, sometimes supplemented by covalent cystine cross links, as in the case of insulin. In many cases, the noncovalent interactions allow more than one conformation and a protein may switch from one conformation to another as part of its function. 

When cyanate is administered to animals, most of the radioactivity is accounted for by carbamylation of NH2-terminal residues of hemoglobin. No detectable carbamylation of lysine or cystine residues is observed. The exact mechanism by which cyanate protects against sickling is not known. Because cyanate... 

Balts increase the solubility is the same as for cystine. However, tiie magnitude of the effect is much greater for hemoglobin. The behavior illustrated in these figures is typical practically every feature of the distinctive solubility of proteins is to be found also in miniature in the study of amino acids. Actually, the knowledge of these phenomena was attained far earlier in the case of the proteins, because they show these effects to a vastly greater extent, so that even the casual observer can scarcely fail to notice them. 

Similar effects are found in solutions of some, but not all, proteins. Thus horse hemoglobin (Richards, 177) and j3-lactoglobulin (E. J. Cohn, J. D. Ferry, and M. H. Blanchard, unpublished studies, quoted in ref. 39, Chapter 24 Gronwall, 85) become decidedly more soluble in the presence of glycine. The relative solvent effect of glycine on these two proteins, and on cystine, asparagine and glycine is shown in Fig. 7 ... 

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