Modification of the single unpaired sulfhydryl group of β-lactoglobulin under high pressure and the role of intermolecular S-S exchange in the pressure denaturation [Single SH of β-lactoglobulin and pressure denaturation]

Chemical modification reactions of the unpaired sulfhydryl group of β-lactoglobulin (LG) under high pressure and the role of this group in the pressure-induced denaturation were investigated. When LG was incubated at 400 MPa (pH 6.8) for 1 h, dimerization through intermolecular reaction of SH was ob...

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Bibliographic Details
Published inInternational journal of biological macromolecules Vol. 19; no. 1; pp. 63 - 68
Main Authors Tanaka, Naoki, Tsurui, Yasuyuki, Kobayashi, Ichizo, Kunugi, Shigeru
Format Journal Article
LanguageEnglish
Published Netherlands Elsevier B.V 01.07.1996
Subjects
Circular Dichroism
Dimerization
Disulfides
Electrophoresis, Polyacrylamide Gel
Fluorescence
High pressure
Irreversible denaturation
Lactoglobulins - chemistry
Pressure
Protein Denaturation
Sulfhydryl Compounds - chemistry
Sulfhydryl group
β-Lactoglobulin
Irreversible denaturation
Sulfhydryl group
Dimerization
β-Lactoglobulin
High pressure
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Summary:Chemical modification reactions of the unpaired sulfhydryl group of β-lactoglobulin (LG) under high pressure and the role of this group in the pressure-induced denaturation were investigated. When LG was incubated at 400 MPa (pH 6.8) for 1 h, dimerization through intermolecular reaction of SH was observed. The generation of the covalently linked dimers were prevented by the presence of N-ethylmaleimide (NEM), an agent for SH-specific modification. The reactivity of the SH group of LG, which is buried inside in its native state, was increased by high pressure, as a result of its exposure to the protein surface accompanied by the pressure denaturation. The effect of NEM was also observed in the fluorescence change caused by high pressure, in both the intrinsic fluorescence of LG and the retinol fluorescence of the LG-retinol complex. The control showed an irreversible change at neutral pH, but it became mostly reversible in the presence of NEM. Compatible results were obtained by CD spectroscopy. Inter- and intramolecular reactions of the SH group are suggested to be main causes for the pressure-induced irreversible denaturation of LG
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ISSN:0141-8130
1879-0003
DOI:10.1016/0141-8130(96)01102-6