Linked Life Data

19699329

Source:http://linkedlifedata.com/resource/pubmed/id/19699329

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
12
pubmed:dateCreated
2009-10-12
pubmed:abstractText
Bovine beta-casein (beta-CN) is a highly amphiphilic micellising phospho-protein showing chaperone-like activity in vitro. Recently, existence of multiple sequential epitopes on beta-CN polypeptide chain in both hydrophilic-polar (psi) and hydrophobic-apolar domains (phi) has been evidenced. In order to clarify specific contribution of polar and apolar domains in micellisation process and in shaping immunoreactivity of beta-CN, its dimeric/bi-amphiphilic "quasi palindromic" forms covalently connected by a disulfide bond linking either N-terminal (C4 beta-CND) or C-terminal domain (C208 beta-CND) were produced and studied. Depending on the C- or N-terminal position of inserted cysteine, each dimeric beta-CN contains one polar/apolar region at the centre and two external hydrophobic/hydrophilic ends. Consequently, such casein dimers have radically different polarities/hydrophobicities on their outside surfaces. Dynamic light scattering (DLS) measurements indicate that these dimeric casein molecules form micelles of different sizes depending on arrangement of polar fragments of the beta-CN mutants in their constrained dimers. Non-aggregated dimers have different hydrodynamic diameters that could be explained by their different geometries. Measurements of fluorescence showed more hydrophobic environment of Trp residues of C208 beta-CND, while in similar experimental conditions Trp residues of C4 beta-CND and native beta-CN were more exposed to the polar medium. Both fluorescence and DLS studies showed greater propensity for micellisation of the dimeric beta-CNs, suggesting that the factors inducing the formation of micelles are stronger in the bi-amphiphilic dimers. 1-anilino-naphthalene-8-sulfonate (ANS) binding studies showed different binding of ANS by these dimers as well as different exposition of ANS binding (hydrophobic) regions in the micellar states. The differences in fluorescence resonance energy transfer (FRET) profiles of C4 beta-CND and C208 beta-CND can be explained by differences of distances and/or by differences of relative orientations of the donor (Trp) and acceptor (ANS), as well as by differences in quenching properties of the disulfide bridges and intra-molecular hydrophobic interactions. The immunoreactivity assays showed somewhat lower IgE response to C208 beta-CND than to C4 beta-CND. Thus, dimerization of C208 beta-CN, connecting two C-terminal hydrophobic domains of two monomers doubling long-range hydrophobic interactions, possibly may hide a part of epitopes in the hydrophobic interface/core of C208 beta-CND that is consistent with the results of DLS and fluorescence studies. The obtained results indicate structural differences of dimers - possibly the formation of Y- and U-shaped structures for C208 beta-CND and C4 beta-CND, respectively. This study not only demonstrated the importance of the organization of polar and hydrophobic regions during micellisation of the constrained and oriented beta-CN dimers but also confirmed a possible role of C-terminal hydrophobic domain in the immunoreactivity profile of native beta-CN.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0006-3002
pubmed:author
pubmed:issnType
Print
pubmed:volume
1794
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1775-83
pubmed:dateRevised
2010-11-18
pubmed:meshHeading
pubmed-meshheading:19699329-Anilino Naphthalenesulfonates, pubmed-meshheading:19699329-Animals, pubmed-meshheading:19699329-Antibody Specificity, pubmed-meshheading:19699329-Caseins, pubmed-meshheading:19699329-Cattle, pubmed-meshheading:19699329-Dimerization, pubmed-meshheading:19699329-Epitopes, pubmed-meshheading:19699329-Fluorescence Resonance Energy Transfer, pubmed-meshheading:19699329-Hydrophobic and Hydrophilic Interactions, pubmed-meshheading:19699329-Immunochemistry, pubmed-meshheading:19699329-Immunoglobulin E, pubmed-meshheading:19699329-Light, pubmed-meshheading:19699329-Micelles, pubmed-meshheading:19699329-Molecular Chaperones, pubmed-meshheading:19699329-Mutagenesis, pubmed-meshheading:19699329-Protein Structure, Quaternary, pubmed-meshheading:19699329-Protein Structure, Tertiary, pubmed-meshheading:19699329-Recombinant Proteins, pubmed-meshheading:19699329-Scattering, Radiation, pubmed-meshheading:19699329-Spectrometry, Fluorescence
pubmed:year
2009
pubmed:articleTitle
Micellisation and immunoreactivities of dimeric beta-caseins.
pubmed:affiliation
UR 1268 Biopolymères Interactions Assemblages, INRA, équipe Fonctions et Interactions des Protéines Laitières, B.P. 71627, 44316 Nantes Cedex 3, France.
pubmed:publicationType
Journal Article, In Vitro, Research Support, Non-U.S. Gov't