Calorimetric Study on the Conformational Transition of α-Lactalbumin Induced by Guanidine Hydrochloride

Okuda, Toshihiko; Sugai, Shintaro

doi:10.1093/oxfordjournals.jbchem.a131527

Cited by 11 publications

(4 citation statements)

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“…Also, Okuda and Sugai (1977) have previously estimated values of 23 and 10 for Anv and AnA, respectively. The excellent agreement between those parameters that have been measured independently with those obtained from the multidimensional analysis provides additional support to the validity of the approach used in this investigation.…”

Section: Resultsmentioning

confidence: 99%

Calorimetric determination of the energetics of the molten globule intermediate in protein folding: apo-.alpha.-lactalbumin

Xie

Bhakuni

Freire³

1991

Biochemistry

122

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High-sensitivity differential scanning calorimetry has been used to characterize the energetics of the molten globule state of apo-alpha-lactalbumin. This characterization has been possible by performing temperature scans at different guanidine hydrochloride (GuHCl) concentrations in order to experimentally define the temperature-GuHCl stability surface of the protein. Multidimensional analysis of the heat capacity surface has allowed simultaneous resolution of the energetics of the unfolded and molten globule states. These experiments indicate that the intrinsic enthalpy difference (i.e., excluding additional contributions such as those arising from differential GuHCl binding) between the unfolded and native states is 31.8 kcal/mol at 25 degrees C whereas that of the molten globule and native states is only 7.7 kcal/mol. At the same temperature, the entropy changes are 99.2 and 23.7 cal/K.mol and the heat capacity changes are 1821 and 326 cal/K.mol, respectively. Analysis of the thermodynamic data indicates that in passing from the native to the molten globule state only approximately 19% of the hydrogen bonds are broken. In addition, the magnitude of delta Cp for the molten globule suggests that water does not largely penetrate into the interior of the molten globule, implying that significant hydrophobic interactions are still present in this state. These parameters provide precise energetic constraints to the allowed structural conformations of the molten globule.

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Section: Resultsmentioning

confidence: 99%

Calorimetric determination of the energetics of the molten globule intermediate in protein folding: apo-.alpha.-lactalbumin

Xie

Bhakuni

Freire³

1991

Biochemistry

122

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“…The following folding scheme of human a-lactalbumin is proposed: Í N Here N is the native form, and the intermediate is a macroscopic state distributed around the state Aq at neutral pH, while the distribution in the acid and fully denatured states shifts toward Am and A-", respectively. Kita et al, 1976;Okuda and Sugai, 1977;Nitta et al, 1977a,b;Kuwajima, 1977) and have characterized it by a variety of methods. The intermediate has been found to be similar to the acid-denatured form, which is also similar to the intermediate forms of carbonic anhydrase and penicillinase.…”

mentioning

confidence: 99%

Detection and characterization of the intermediate on the folding pathway of human .alpha.-lactalbumin

Nozaka¹,

Kuwajima²,

Nitta³

et al. 1978

Biochemistry

Self Cite

106

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To discuss the relation between the folding mechanism and the chemical structure of proteins, the reversible unfolding reactions of human alpha-lactalbumin by acidification and by guanidine hydrochloride at 25 degrees C are studied by means of circular dichroism, difference spectra and pH-jump measurements and are compared with those for bovine alpha-lactalbumin. As shown previously for bovine alpha-lactalbumin, the folding process at neutral pH is not explained by a simple two-state mechanism but involves an intermediate form that has the same amount of helical structures as the native form. The transition between the intermediate and the fully denatured states is too rapid to be measured and corresponds to the helix-coil transition of the backbone. One of the differences of human alpha-lactalbumin from the bovine protein is the remarkable stability of the intermediate at neutral pH, which can be explained by differences in the primary chemical structure. Another difference is the existence at acid pH of an additional helical form, which is more helical than the native form. The transition from this to the intermediate or to the fully denatured one also is shown to resemble the helix-coil transition. The following folding scheme of human alpha-lactalbumin is proposed: formula: (see text). Here N is the native form, and the intermediate is a macroscopic state distributed around the state A3 at neutral pH, while the distribution in the acid and fully denautured states shifts toward Am and A-n, respectively.

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“…Lysozyme, a small monomeric protein of 129 residues, is one of the earliest characterized and most studied globular proteins. − On the other hand, α-lactalbumin, with 123 residues, has been targeted because of the striking similarity to lysozyme. Indeed, α-lactalbumin has high sequence homology and a closely similar folded structure to lysozyme. − …”

Section: Resultsmentioning

confidence: 99%

“…Lysozyme − and α-lactalbumin − are homologous proteins. These proteins, which have similar low helicities, adopt more helical structures in the SDS solutions, and then they have two types of helices at 25 °C: the original helices and the SDS-induced helices.…”

Section: Introductionmentioning

confidence: 99%

Secondary Structural Changes of Homologous Proteins, Lysozyme and α-Lactalbumin, in Thermal Denaturation up to 130 °C and Sodium Dodecyl Sulfate (SDS) Effects on These Changes: Comparison of Thermal Stabilities of SDS-Induced Helical Structures in These Proteins

2012

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The thermal stability of two homologous proteins, lysozyme and α-lactalbumin, was examined by circular dichroism. The present study clearly showed two different aspects between the homologous proteins: (1) the original helices of lysozyme and α-lactalbumin were unchanged at heat treatments up to 60 and 40 °C, respectively, indicating a higher thermal stability of lysozyme, and (2) upon cooling to 25 °C, the original helices of lysozyme were never reformed after they were once disrupted, while those of α-lactalbumin, disrupted at a particular temperature range between 40 and 60 °C, were completely reformed. In addition, the structural changes were also examined in the coexistence of sodium dodecyl sulfate (SDS), which induced the formation of helical structures in these proteins at 25 °C. A distinct difference appeared in the thermal stabilities of the SDS-induced helices. All of the SDS-induced helices of lysozyme were disrupted below 60 °C, while those of α-lactalbumin at 10 mM SDS were unchanged up to 130 °C. A similarity was also fixed. Not only the SDS-induced helices but also the original helices of the two proteins were reformed upon cooling to 25 °C after the thermal denaturation below 100 °C in the coexistence of 10 mM SDS.

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Calorimetric Study on the Conformational Transition of α-Lactalbumin Induced by Guanidine Hydrochloride

Cited by 11 publications

References 0 publications

Calorimetric determination of the energetics of the molten globule intermediate in protein folding: apo-.alpha.-lactalbumin

Calorimetric determination of the energetics of the molten globule intermediate in protein folding: apo-.alpha.-lactalbumin

Detection and characterization of the intermediate on the folding pathway of human .alpha.-lactalbumin

Secondary Structural Changes of Homologous Proteins, Lysozyme and α-Lactalbumin, in Thermal Denaturation up to 130 °C and Sodium Dodecyl Sulfate (SDS) Effects on These Changes: Comparison of Thermal Stabilities of SDS-Induced Helical Structures in These Proteins

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