Lysozyme guanidine hydrochloride

Titration studies of lysozyme have revealed two unique features, both occurring in the carboxyl region of the titration curve. The pertinent data are shown in Table XIV. It is seen (o) that the count of carboxyl groups varies widely from one preparation of lysozyme to another, and (5) that three extra carboxyl groups appear in denaturing solvents such as 8 Af guanidine hydrochloride. 

The behaviors of apo- and Ca(Il)-bound forms of a-lactalbumin differ markedly upon denaturation with guanidine hydrochloride, as shown by Ikeguchi et al. (1986). Thus, at low Ca(ll) ion concentration a-lactalbumin unfolds to produce a stable intermediate, while at high Ca(ll) concentration the protein unfolds in a manner similar to that of lysozyme. 

Greene, R. F. and C. N. Pace. 1974. Urea and guanidine-hydrochloride denaturation of ribonuclease, lysozyme, a-chymotrypsin, and P-lactoglobuhn. Journal of Biological Chemistry. 249, 5388. 

In some cases the products of thermal denaturation are not completely unfolded and retain structured regions. The addition of guanidine hydrochloride often induces another transition. This has been described for ribonuclease, chymotrypsinogen, and lysozyme (Tanford, 1968). 

Phage T4 lysozyme is a small protein of MW 18,700 and is devoid of disulfide bridges (Fig. 5.6A). For this protein, reversibility of unfoldingfolding was reported under different conditions, either after thermal unfolding or after denaturation by guanidine hydrochloride (Elwell and Schellmann, 1975, 1977 Elwell, 1976 Desmadril and Yon, 1981). Reversibility was checked by different techniques which included fluorescence emission, CD at 223 nm and in aromatic region, and some enzymatic assays. 

Fig. 6.10. Guanidine hydrochloride dena-turation of lysozyme. Curves are drawn according to the equation AG = AGq (1 + olK) with a = 0.35 for curve 1 a = 0.275 for curve 2 (from Tanford, 1970).

Fig. 19. Unfolding and foldit rates of lysozyme in guanMine hydrochloride solution at neutral pH, determine by Tanford, Pain and Otchin ( 5). For conditions (i.e. guanidine hydrochlorkle concentrations) where k /k( ( () differs greatly from unity, the higher rate was determiiKd experimenUdly, the lower calculated from the equilibrium constant for unfolding whidi, itself was calculated by extrapolation of equilibrium transition data, if necessary. (Units are k in sec Cc Ha...

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