Mar 18, 1976

Equilbrium and kinetics of the unfolding of alpha-lactalbumin by guanidine hydrochloride (II)

Biochimica Et Biophysica Acta
N KitaS Sugai

Abstract

The reversible unfolding of alpha-lactalbumin by guanidine hydrochloride, was studied at 25.0 degrees C in a relatively low concentration range of the denaturant (0.80-2.00 mol/l) by means of difference spectra and pH-jump measurements. The unfolding was shown to occur between two states, N and D, because apparent rate-constants of the unfolding and the refolding reactions depended only on pH. All curves plotted as the logarithmical equilibrium constant log KD against pH could fall on the same base curve by shifting each curve along the log KD axis. From the dependence of the logarithmic rate constant on pH, master curves could also be made for the forward and the backward reactions. The dependence of these master curves on pH indicates that the groups affecting the pH dependence of the unfolding are three residues with pKN = 3.3 and pKA = pKD = 4.4, one residue with pKN = pKA = 3.8 and pKD = 4.4, and one residue with pKN = 5.8 and pKA = pKD = 6.3, where A indicates the activated state. On the other hand, from the denaturant activity dependence of the shift factors required for making the master curves, the value of the intrinsic binding constant of the denaturant to the protein was found to be similar to that obtained from pre...Continue Reading

Mentioned in this Paper

Mucocutaneous Lymph Node Syndrome
Lysozyme Test
Plasma Protein Binding Capacity
Lysozyme
Muramidase
Protein Conformation
Guanidine Hydrochloride
Guanidines
Bos indicus
LALBA

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