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κ-Casein terminates casein micelle build-up by its "soft" secondary structure.
MedLine Citation:
PMID:  23015063     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
In our previous paper (Nagy et al. in J Biol Chem 285:38811-38817, 2010) by using a multilayered model system, we showed that, from α-casein, aggregates (similar to natural casein micelles) can be built up step by step if Ca-phosphate nanocluster incorporation is ensured between the protein adsorption steps. It remained, however, an open question whether the growth of the aggregates can be terminated, similarly to in nature with casein micelles. Here, we show that, in the presence of Ca-phosphate nanoclusters, upon adsorbing onto earlier α-casein surfaces, the secondary structure of α-casein remains practically unaffected, but κ-casein exhibits considerable changes in its secondary structure as manifested by a shift toward having more β-structures. In the absence of Ca-phosphate, only κ-casein can still adsorb onto the underlying casein surface; this κ-casein also expresses considerable shift toward β-structures. In addition, this κ-casein cover terminates casein aggregation; no further adsorption of either α- or κ-casein can be achieved. These results, while obtained on a model system, may show that the Ca-insensitive κ-casein can, indeed, be the outer layer of the casein micelles, not only because of its "hairy" extrusion into the water phase, but because of its "softer" secondary structure, which can "occlude" the interacting motifs serving casein aggregation. We think that the revealed nature of the molecular interactions, and the growth mechanism found here, might be useful to understand the aggregation process of casein micelles also in vivo.
Authors:
Krisztina Nagy; György Váró; Balázs Szalontai
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-9-27
Journal Detail:
Title:  European biophysics journal : EBJ     Volume:  -     ISSN:  1432-1017     ISO Abbreviation:  Eur. Biophys. J.     Publication Date:  2012 Sep 
Date Detail:
Created Date:  2012-9-27     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8409413     Medline TA:  Eur Biophys J     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Institute of Biophysics, Biological Research Centre, Hungarian Academy of Sciences, P.O.B. 521, Szeged, 6701, Hungary.
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