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Influence of the protein conformation on the interaction between α-lactalbumin and dimyristoylphosphatidylcholine vesicles

1985; Elsevier BV; Volume: 817; Issue: 1 Linguagem: Inglês

10.1016/0005-2736(85)90078-1

1879-2642

Ignace Hanssens, Jean-Claude van Ceuncbroeck, Hans Pottel, Gisèle Préaux, Frans Van Cauwelaert,

Glycosylation and Glycoproteins Research

α-Lactalbumin is a globular protein containing helical regions with highly amphiphathic character. In this work, the interaction between bovine α-lactalbumin and sonicated dimyristoylphosphatidylcholine vesicles has been compared in different circumstances which influence the protein conformation i.e., pH, ionic strength, decalcification, guanidine hydrochloride denaturation. Above the isoelectric point the interaction is mainly electrostatic; improved electrostatic interaction results in better contact with the apolar lipid phase. Below the isoelectric point, hydrophobic forces dominate the interaction and the vesicles are solubilized. The mode of interaction is not determined to a great extent by the demetallization of the protein. However, by a more explicit unfolding of the globular structure with guanidine hydrochloride, micellar complexes can be formed with the lipid, even at neutral pH. From this study it is obvious that the presence or capability for formation of helices with high amphipathic character is not a sufficient condition for lipid solubilization by a globular protein. Also, the capability of a globular protein to unfold its tertiary structure seems to be a prerequisite for its capability to lipid solubilization.