Molten globule state of equine beta-lactoglobulin.
Abstract: The acid-unfolded state of equine beta-lactoglobulin was characterized by means of circular dichroism, nuclear magnetic resonance, analytical gel-filtration chromatography, and analytical centrifugation. The acid-unfolded state of equine beta-lactoglobulin has a substantial secondary structure as shown by the far-ultraviolet circular dichroism spectrum but lacks persistent tertiary packing of the side chains as indicated by the near-ultraviolet circular dichroism and nuclear magnetic resonance spectra. It is nearly as compact as the native conformation as shown by the gel filtration and sedimentation experiments, and it has the exposed hydrophobic surface as indicated by its tendency to aggregate. All of these characteristics indicate that the acid-unfolded state of equine beta-lactoglobulin is a molten globule state. The alpha helix content in the acid-unfolded state, which has been estimated from the circular dichroism spectrum, is larger than that in the native state, suggesting the presence of nonnative alpha helices in the molten globule state. This result suggests the generality of the intermediate with nonnative alpha helices during the folding of proteins having the beta-clam fold.
Publication Date: 1997-04-01 PubMed ID: 9141136DOI: 10.1002/(sici)1097-0134(199704)27:4<567::aid-prot9>3.0.co;2-7Google Scholar: Lookup
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- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research investigates the characteristics of the acid-unfolded state of equine beta-lactoglobulin, concluding that it primarily exists in a molten globule state. It also indicates that there may exist nonnative alpha helices within this molten globule state.
Characterization of the Acid-Unfolded State
- The researchers used circular dichroism, nuclear magnetic resonance, and chromatography-based methods to examine the acid-unfolded state of equine beta-lactoglobulin.
- Observations from these tests indicate that the unfolded protein retains a significant level of secondary structure, demonstrated by the far-ultraviolet circular dichroism spectrum.
- The protein lacks consistent tertiary side chain packing, as suggested by near-ultraviolet circular dichroism and NMR spectra.
Molten Globule State Presence
- Sedimentation and gel filtration experiments exhibit nearly the same compactness as the beta-lactoglobulin’s native conformation.
- The protein also displayed an exposed hydrophobic surface that showed a tendency to aggregate, a significant characteristic of molten globule states.
Alpha Helix Content
- The researchers measured the alpha helix content within the acid-unfolded state, which appeared to be larger than that in the native beta-lactoglobulin state.
- This quantification was done utilizing information from the circular dichroism spectrum.
- The significant presence of the alpha helix configuration suggests the existence of nonnative alpha helices within the molten globule state.
Implications for Protein Folding
- This finding generally suggests the presence of an intermediate form with nonnative alpha helices during the protein folding process specific to proteins with the beta-clam fold.
Cite This Article
APA
Ikeguchi M, Kato S, Shimizu A, Sugai S.
(1997).
Molten globule state of equine beta-lactoglobulin.
Proteins, 27(4), 567-575.
https://doi.org/10.1002/(sici)1097-0134(199704)27:4<567::aid-prot9>3.0.co;2-7 Publication
Researcher Affiliations
- Department of Bioengineering, Faculty of Engineering, Soka University, Tokyo, Japan.
MeSH Terms
- Acids
- Amino Acid Sequence
- Animals
- Chromatography, Gel
- Circular Dichroism
- Horses
- Hydrogen-Ion Concentration
- Lactoglobulins / chemistry
- Magnetic Resonance Spectroscopy
- Molecular Sequence Data
- Particle Size
- Protein Folding
- Protein Structure, Secondary
- Retinol-Binding Proteins / chemistry
- Sequence Homology, Amino Acid
- Species Specificity
- Ultracentrifugation
Citations
This article has been cited 15 times.- Ikeguchi M. Transient non-native helix formation during the folding of β-lactoglobulin. Biomolecules 2014 Feb 13;4(1):202-16.
- Matsumura Y, Shinjo M, Kim SJ, Okishio N, Gruebele M, Kihara H. Transient helical structure during PI3K and Fyn SH3 domain folding. J Phys Chem B 2013 May 2;117(17):4836-43.
- Matsumura Y, Shinjo M, Matsui T, Ichimura K, Song J, Kihara H. Structural study of hNck2 SH3 domain protein in solution by circular dichroism and X-ray solution scattering. Biophys Chem 2013 May-Jun;175-176:39-46.
- Mercadante D, Melton LD, Norris GE, Loo TS, Williams MA, Dobson RC, Jameson GB. Bovine β-lactoglobulin is dimeric under imitative physiological conditions: dissociation equilibrium and rate constants over the pH range of 2.5-7.5. Biophys J 2012 Jul 18;103(2):303-12.
- Ohtomo H, Konuma T, Utsunoiya H, Tsuge H, Ikeguchi M. Structure and stability of Gyuba, a β-lactoglobulin chimera. Protein Sci 2011 Nov;20(11):1867-75.
- Viseu MI, Carvalho TI, Costa SM. Conformational transitions in beta-lactoglobulin induced by cationic amphiphiles: equilibrium studies. Biophys J 2004 Apr;86(4):2392-402.
- Sakurai K, Oobatake M, Goto Y. Salt-dependent monomer-dimer equilibrium of bovine beta-lactoglobulin at pH 3. Protein Sci 2001 Nov;10(11):2325-35.
- Fujiwara K, Ikeguchi M, Sugai S. A partially unfolded state of equine beta-lactoglobulin at pH 8.7. J Protein Chem 2001 Feb;20(2):131-7.
- Carrotta R, Bauer R, Waninge R, Rischel C. Conformational characterization of oligomeric intermediates and aggregates in beta-lactoglobulin heat aggregation. Protein Sci 2001 Jul;10(7):1312-8.
- Bedell JL, McCrary BS, Edmondson SP, Shriver JW. The acid-induced folded state of Sac7d is the native state. Protein Sci 2000 Oct;9(10):1878-88.
- Sakai K, Sakurai K, Sakai M, Hoshino M, Goto Y. Conformation and stability of thiol-modified bovine beta-lactoglobulin. Protein Sci 2000 Sep;9(9):1719-29.
- Sheshadri S, Lingaraju GM, Varadarajan R. Denaturant mediated unfolding of both native and molten globule states of maltose binding protein are accompanied by large deltaCp's. Protein Sci 1999 Aug;8(8):1689-95.
- Blanch EW, Hecht L, Barron LD. New insight into the pH-dependent conformational changes in bovine beta-lactoglobulin from Raman optical activity. Protein Sci 1999 Jun;8(6):1362-7.
- Kendrick BS, Carpenter JF, Cleland JL, Randolph TW. A transient expansion of the native state precedes aggregation of recombinant human interferon-gamma. Proc Natl Acad Sci U S A 1998 Nov 24;95(24):14142-6.
- Yanagida Y, Yoshida K, Ohtomo M, Fujiwara K, Ikeguchi M. Mechanisms of helix induction by the closed loop. Protein Sci 2025 Jun;34(6):e70171.
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