Free energy changes in .alpha.-lactalbumin denaturation

Contaxis, C. C.; Bigelow, Charles C.

doi:10.1021/bi00509a032

Cited by 16 publications

(6 citation statements)

References 9 publications

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“…ture, for D(LiC104)-RNase, are shown in Figure5. Both vary linearly with temperature (in the range of 4-64 °C) and exhibit no evidence of a conformational transition; similar ob-h i b i t e d .TableI: Comparison of the Conformational Behavior of D(LiC104)-RNase and D(pH)Ahmad & Bigelow (1979) and this paper for DfLiClO^-RNase andKuwajima et al (1976),Contaxis & Bigelow (1981),and Dolgikh et al (1981) for D(pH)-a-lactalbumin.…”

supporting

confidence: 59%

“…Acetic acid greatly decreases the amplitude of the aromatic CD spectrum of tyrosine but affects the backbone CD spectrum of native RNase only slightly (Cann, 1971); this indicates that D(acetic acid)-RNase1 has some ordered backbone structure but disordered tyrosine side-chain conformations. Similarly, ordered structures have been observed for -lactalbumin denatured by lowering the pH [D(pH)-a-lactalbumin]1 (Kuwajima et al, 1976); the CD spectrum of the backbone was analyzed in terms of contributions from a helix, ß structure, and random coil, with the suggestion that D(pH)-a-lactalbumin appears to have a higher -helix but a lower /3-structure content than the native protein (Kuwajima, 1977;Contaxis & Bigelow, 1981). Neutral salts can act similarly to produce denatured proteins with some ordered structure (von Hippel & Schleich, 1969); many different kinds of neutral salts have been found to denature RNase (von Hippel & Wong, 1965; Ahmad & Bigelow, 1979), and the CD spectra of denatured RNase indicated that LiClG4 was the most effective in disordering the tyrosine side chains without inducing much change in the backbone structure.…”

mentioning

confidence: 97%

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Folding of ribonuclease A from a partially disordered conformation. Kinetic study under folding conditions

Denton¹,

Konishi²,

Scheraga³

1982

Biochemistry

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Bovine pancreatic ribonuclease A (RNase) was partially disordered with 3.5 M LiClO4 (pH 3.0). The conformation of this partially disordered material was studied by circular dichroism and Raman spectroscopy. Although the partially disordered protein appears to have a lower beta-structure content and disordered tyrosyl side chains, compared to native RNase, it seems to retain some ordered backbone structure that is suggested to be alpha helix. The kinetics of folding of LiClO4-denatured RNase was studied by means of absorption and circular dichroism measurements. For comparison, the kinetics of folding of urea-denatured RNase (which is completely devoid of ordered structure) was examined with the same techniques. Since the kinetics of folding of both denatured species are found to be similar, it appears that the ordered structure present in LiClO4-denatured RNase plays no role in determining the folding pathway. Also, the change in the circular dichroism at 220 nm showed that some of the ordered structure in LiClO4-denatured RNase becomes disordered in the early stages of folding. This implies that all ordered structures in RNase are not equivalent in their influence on the folding pathway; some can play an essential role and some may not.

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supporting

confidence: 59%

mentioning

confidence: 97%

Folding of ribonuclease A from a partially disordered conformation. Kinetic study under folding conditions

Denton¹,

Konishi²,

Scheraga³

1982

Biochemistry

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“…The first most convincing evidence for the presence of native-like residual structure in the heat denatured state of proteins came from Tanford and associates [ 19 ] who observed another cooperative transition between heat-denatured (X) state and GdmCl denatured (D) state on adding GdmCl to already heat-denatured proteins. (Latter many studies supported this observation (see, e.g., [ 8 , 20 , 21 , 22 ]).) All these studies led to the conclusion that the heat denatured state of proteins are less unfolded than the GdmCl-induced denatured state.…”

Section: Introductionmentioning

confidence: 87%

Cooperative Unfolding of Residual Structure in Heat Denatured Proteins by Urea and Guanidinium Chloride

et al. 2015

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The denatured states of proteins have always attracted our attention due to the fact that the denatured state is the only experimentally achievable state of a protein, which can be taken as initial reference state for considering the in vitro folding and defining the native protein stability. It is known that heat and guanidinium chloride (GdmCl) give structurally different states of RNase-A, lysozyme, α-chymotrypsinogen A and α-lactalbumin. On the contrary, differential scanning calorimetric (DSC) and isothermal titration calorimetric measurements, reported in the literature, led to the conclusion that heat denatured and GdmCl denatured states are thermodynamically and structurally identical. In order to resolve this controversy, we have measured changes in the far-UV CD (circular dichroism) of these heat-denatured proteins on the addition of different concentrations of GdmCl. The observed sigmoidal curve of each protein was analyzed for Gibbs free energy change in the absence of the denaturant (ΔG 0 X→D) associated with the process heat denatured (X) state ↔ GdmCl denatured (D) state. To confirm that this thermodynamic property represents the property of the protein alone and is not a manifestation of salvation effect, we measured urea-induced denaturation curves of these heat denatured proteins under the same experimental condition in which GdmCl-induced denaturation was carried out. In this paper we report that (a) heat denatured proteins contain secondary structure, and GdmCl (or urea) induces a cooperative transition between X and D states, (b) for each protein at a given pH and temperature, thermodynamic cycle connects quantities, ΔG 0 N→X (native (N) state ↔ X state), ΔG 0 X→D and ΔG 0 N→D (N state ↔ D state), and (c) there is not a good enthalpy difference between X and D states, which is the reason for the absence of endothermic peak in DSC scan for the transition, X state ↔ D state.

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“…The primary structure of bovine a-Iactalbumin has been established (Brew et al, 1970). The conformation of this protein is pH-dependent (Kronman et al, 1965;Kuwajima, 1977;Contaxis & Bigelow, 1981). Bovine ao lactalbumin is resistant to in vitro proteolysis by pepsin at pH 6.0, which is the pH of calf abomasum contents immediately after feeding milk, but is degraded at pH 2.0 (Jenkins et al, 1980).…”

Section: Introductionmentioning

confidence: 99%

Hydrolysis of α-lactalbumin by chymosin and pepsin. Effect of conformation and pH

Miranda

Haze

Scanff

et al. 1989

Lait

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Summary -The correlation between change of conformation of a-Iactalbumin and its degradation by gastric enzymes was verified. With citrate buffer (0.1 M), the modification of a-Iactalbumin conformation occurred when the pH value was below pH 4.0. This conformational change was influenced by buffer composition and ionic strength. However, the presence of EDTA in the butter did not modify the pH value at which the change of conformation of the protein occurred. Concomitantly, hydrolysis of a-Iactalbumin by bovine and porcine pepsins A and rennet was observed at pH values corresponding to the change in conformation of the protein. However, with chymosin, under the same pH and ionie strength conditions there was no significant hydrolysis of a-Iactalbumin.

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Free energy changes in .alpha.-lactalbumin denaturation

Cited by 16 publications

References 9 publications

Folding of ribonuclease A from a partially disordered conformation. Kinetic study under folding conditions

Folding of ribonuclease A from a partially disordered conformation. Kinetic study under folding conditions

Cooperative Unfolding of Residual Structure in Heat Denatured Proteins by Urea and Guanidinium Chloride

Hydrolysis of α-lactalbumin by chymosin and pepsin. Effect of conformation and pH

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