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Journal of protein chemistry2001; 20(2); 131-137; doi: 10.1023/a:1011029524100

A partially unfolded state of equine beta-lactoglobulin at pH 8.7.

Abstract: The urea-induced unfolding transition of equine beta-lactoglobulin was studied at pH 8.7 using circular dichroism (CD), ultracentrifugation, and gel filtration chromatography. The unfolding transition curves showed that at least one intermediate accumulates at moderate concentrations of urea. Furthermore, analytical ultracentrifugation experiments indicated that the intermediate forms a dimer. Thus, the urea-induced unfolding transition was measured by CD at various protein concentrations and was analyzed by a model assuming the four conformational states (the native, intermediate, dimeric intermediate, and unfolded states). The characteristics of the intermediate are markedly different from those of the intermediate previously observed at pH 4.0 or 1.5. The intermediate at pH 8.7 does not show the intense far-ultraviolet CD suggestive of the nonnative alpha-helix.
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Publication Date: 2001-09-21 PubMed ID: 11563693DOI: 10.1023/a:1011029524100Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The researchers have studied the process of unfolding of a protein called equine beta-lactoglobulin under certain conditions using various techniques. They have discovered that during this process, an intermediary, unique structure forms that is different from those formed under different conditions.

Methodology of the Research

  • The researchers are investigating the process of unfolding of a protein called equine beta-lactoglobulin that occurs when it is exposed to urea, under the conditions of pH 8.7.
  • They employed several scientific techniques to explore this process including circular dichroism (CD), ultracentrifugation and gel filtration chromatography.
  • Circular Dichroism is a spectrometry method that measures the differences in the absorption of right-handed and left-handed circularly polarised light, hence providing a measure of the secondary structure of the protein.
  • Ultracentrifugation and gel filtration chromatography are both methods used to separate molecules, in this case separating the different states of the protein during the unfolding process.

Key Findings

  • The study found that the urea-induced unfolding of this protein is not a simple process but one that involves the formation of intermediary structures or states during the transition from the native folded state to the completely unfolded state.
  • At moderate concentrations of urea, an intermediary state is formed which is capable of forming a dimer, or in other words, two copies of this structure can bind together to form a complex.
  • The researchers used a model that assumes the existence of four conformational states – the native state, an intermediate state, a dimeric intermediate state, and the unfolded state – to analyze the results.

Uniqueness of the Intermediate State

  • The properties of the intermediate state observed at pH 8.7 are considerably different from the intermediate states observed at more acidic conditions (pH 4.0 or 1.5).
  • In particular, the intermediate at pH 8.7 does not show any strong CD signal in the far-ultraviolet region, suggesting that it does not contain any non-native alpha-helix structures, unlike the intermediates formed at other pH levels.

Implications of the Research

  • This research gives us a better understanding of the complex unfolding process of the protein equine beta-lactoglobulin under different conditions, which could have implications for understanding the behavior of this protein in various biological contexts.
  • The unique nature of the intermediate state observed in this study at pH 8.7 suggests that the conformational state of the protein and its unfolding pathway can be significantly affected by the surrounding conditions such as pH and the presence of other molecules like urea.

Cite This Article

APA
Fujiwara K, Ikeguchi M, Sugai S. (2001). A partially unfolded state of equine beta-lactoglobulin at pH 8.7. J Protein Chem, 20(2), 131-137. https://doi.org/10.1023/a:1011029524100

Publication

Journal of protein chemistry
ISSN: 0277-8033
NlmUniqueID: 8217321
Country: United States
Language: English
Volume: 20
Issue: 2
Pages: 131-137

Researcher Affiliations

Fujiwara, K
  • Department of Bioengineering, Faculty of Engineering, Soka University, Hachioji, Tokyo, Japan.
Ikeguchi, M
    Sugai, S

      MeSH Terms

      • Animals
      • Cattle
      • Circular Dichroism
      • Dimerization
      • Horses
      • Hydrogen-Ion Concentration
      • Lactoglobulins / chemistry
      • Lactoglobulins / drug effects
      • Protein Denaturation / drug effects
      • Protein Folding
      • Spectrometry, Fluorescence / methods
      • Urea / pharmacology

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      Citations

      This article has been cited 1 times.
      1. Fernandez NF, Sansone S, Mazzini A, Brancaleon L. Irradiation of the porphyrin causes unfolding of the protein in the protoporphyrin IX/beta-lactoglobulin noncovalent complex. J Phys Chem B 2008 Jun 26;112(25):7592-600.
        doi: 10.1021/jp710249dpubmed: 18517238google scholar: lookup
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