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Interactions of gamma-immunoglobulins with lipid mono- or bilayers and liposomes. Existence of two conformations of gamma-immunoglobulins of different hydrophobicities.

par Vandenbranden, Michel ;De Coen, Jean-Louis ;Jeener, Raymond ;Kanarek, L;Ruyschaert, J-M
Référence Molecular immunology, 18, 7, page (621-631)
Publication Publié, 1981-07

Article révisé par les pairs

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Résumé :

Interactions between rabbit-γ-immunoglobulins and model membranes (lipid monolayers, 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.