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Pressure-temperature stability, Ca2+-binding and p-T phase diagram of cod parvalbumin: Gad m 1.
MedLine Citation:
PMID:  22765301     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Fish allergy is associated with IgE-mediated hypersensitivity reactions to parvalbumins, which are small calcium-binding muscle proteins and represent the major and sole allergens for 95% of fish-allergic patients. We performed Fourier transform infrared and tryptophan fluorescence spectroscopy to explore the p-T phase diagram of cod parvalbumin (Gad m 1) and to elucidate possible new ways of pressure-temperature inactivation of this food allergen. Besides the secondary structure of the protein the Ca2+-binding to aspartic and glutamic acid residues was detected. The phase diagram was found to be quite complex containing partially unfolded and molten globule states. The Ca2+ ions were essential for the formation of the native structure. A molten globule conformation appears at 50 °C and atmospheric pressure, which converts into an unordered aggregated state at 75 °C. Above 200 MPa only heat unfolding, but no aggregation was observed. A pressure of 500 MPa leads to a partially unfolded state at 27 °C. The complete pressure unfolding could only be reached at elevated temperature (40 °C) and pressure 1.14 GPa. A strong correlation was found between Ca2+-binding and the protein conformation. The partially unfolded state was reversibly refolded. The completely unfolded molecule, however, where Ca2+ was released, could not refold. The heat-unfolded protein was trapped either in the aggregated state or in the molten globule state with an absence of aggregation at elevated pressure. The heat and the combined heat and pressure treated protein samples were tested with sera of allergic patients, but no change in the allergenicity was found.
Authors:
Judit Somkuti; Merima Bublin; Heimo Breiteneder; Laszlo Smeller
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-7-5
Journal Detail:
Title:  Biochemistry     Volume:  -     ISSN:  1520-4995     ISO Abbreviation:  -     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-7-6     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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