Conalbumin, denaturation

Fig. 13. Viscosity changes accompanying the denaturation and "renaturation of conalbumin at pH 6.0. A, Conalbumin (0.5 g/100 ml) in 6 M urea (0.05 M NaCl) B, Solution A diluted with an equal volume of 0.05 M NaCl. (Biochim. Biophys. Acta 71, 109 [1963]).

Table 11. Properties of native, denatured and "renatured conalbumin in 0.05 M NaCl, at the pH indicated...

Atari, P. R. and R. E. Feeney Resistance of metal complexes of conalbumin and transferrin to proteolysis and to thermal denaturation. J. Biol. Chem. 232, 293 (1958). 

Wu, H. and S. M. Ling Denaturation of proteins. V. Factors controlling coagulation of proteins by shaking. Separation of ovalbumin from conalbumin. Chinese J. Physiol. I, 407 (1927). 

Conalbumin In acid and urea denaturation, UV A-spectral changes are more rapid than those in a, ij, and the visible spectrum Glazer and McKenzie (1962b)... 

Conalbumin (Warner, 1954) appears to duplicate very closely not only the unmasking effects reported for the hemoglobins and globin, but also the kinetics and equilibria involved in the reversal process of denaturation which accompanies unmasking and which are described later. 

Avidin a basic glycoprotein in the egg whites of many birds and amphibians. The primary structure of chicken A. is known M, 66,000, pi 10, 10.5 % threonine. There are 4 identical subunits of M, 14332 (without the carbohydrate) (128 amino acids). A. forms a stoichiometric, noncovalent complex with 4 molecules of the vitamin, biotin the complex is not attacked by proteolytic enzymes and therefore not resorbed. Feeding of A. or raw egg white can therefore result in experimental biotin deficiency (see Vitamins, biotin). A. is denatured and thus inactivated by heating. Like the unrelated lysozyme and conalbumin (see Siderophilins), A. protects the egg white against bacterial invasion. 

Egg white is a solution in water, 12% solids, primarily the glycoproteins (protein joined to a carbohydrate) ovalbumin (57%) and conalbumin, and a number of other proteins, with molecular weights of 10,000-70,000. Some of the proteins denature and coagulate on heating. On drying, egg white becomes... 

Conalbumin and serum transferrin are identical in the chicken. This protein, unlike ovalbumin, is not denatured at the interphase but coagulates at lower temperatures. Conalbumin consists of one peptide chain and contains one oligosaccharide unit made of four mannose and eight N-acetyl-glucosamine residues. 

In the study of egg white and its components [104], it was found that thermostability was in the order ovalbumin > lysozyme > conalbumin and that lowering the pH from 9 to 7, adding AP+ ions or sucrose increased the stability of these proteins as indicated by shifts of the endotherms to higher temperatures. Heat treatment of myoglobin at low moisture content suggested that only part of the protein was undergoing denaturation, resulting in apparent increases in heat stability and decrease in solubility [105]. 

---