Interactions of γ-immunoglobulins with lipid mono- or bilayers and liposomes. Existence of two conformations of γ-immunoglobulins of different hydrophobicities |
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Authors: | M. Vandenbranden J.L. de Coen R. Jeener L. Kanarek J.M. Ruyschaert |
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Affiliation: | 1. Laboratoire de Chimie-Physique des Macromolecules aux Interfaces, Université Libre de Bruxelles, BrusselBelgium;2. Laboratoire de Chimie Biologique, Faculté des Sciences, Université Libre de Bruxelles, BrusselBelgium;3. Laboratoire de Physiologie Animale, Université Libre de Bruxelles, BrusselBelgium;4. Laboratorium voor Chemie der Proteinen, Vrije Universiteit, BrusselBelgium |
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Abstract: | Interactions between rabbit-γ-immunoglobulins and model membranes (lipid monalayers, planar lipid bilayers, liposomes) have been investigated. No significant interaction was observed with immunoglobulins. However, immunoglobulins dialysed first vs aqueous buffer having pH 2 or 3 and then dialysed against pH 7 buffer presumably adopt a new conformation which allows their bindings to model membranes. This binding is hydrophobic and the immunoglobulin region interacting with the lipid acyl chains is probably located in the heavy chain, as suggested by labelling in this region by a photosensitive probe previously incorporated into the lipid hydrophobic core. Cleavage at the hinge region by papain or pepsin, or heating above 38°C, induces the loss of the hydrophobic conformation responsible for hydrophobic bindings. The binding capacity of immunoglobulins heated above 38°C is restored after momentary dialysis at pH 2. The possible existence of two Ig isomers is discussed in relation to the mechanism of γ-immunoglobulin passage through the endoplasmic membrane and fixation into the plasma membrane. |
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Keywords: | PC buffer PC-HC1 buffer pH 2 buffer obtained by addition of aliquots of concentrated HC1 to a pH 3 PC buffer DPPC DMPC CL cardiolipin (diphosphatidyl glycerol) DPPE egg PC phosphatidylcholine from egg yolk PS phosphatidyl serine SPH sphingomyelin DEAE diethylaminoethyl ANS 8-anilinonaphthalene 1-sulfonate SDS sodium dodecyl sulfate FITC fluorescein isothiocyanate CM cellulose carboxymethylcellulose CD circular dichroism |
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