Penetration of human apolipoprotein H into air/water interface with and without phospholipid monolayers

Apolipoprotein I-I (beta(2)-glycoprotein I) is a 54 kDa plasma glycoprotein . The interaction of ApoH with phospholipids has been demonstrated to be in volved in the regulation of the function of the activated platelets and the clearance of phosphotidylserine (PS)-expressing cells. In the present work , the monolayer technique is employed to characterize the feature of the pe netration of ApoH into air/water interface with and without phospholipid mo nolayers. The results indicate that ApoH can penetrate into the air/water i nterface and there is a protein-concentration dependent lag time in the ads orption isotherm. ApoH can insert into the phospholipid monolayers spread a t the air/water interface, but no lag time is observed in this case. The fa ct that ApoH prefers to interact with anionic phospholipid monolayers sugge sts that the negative charges of the phospholipid monolayers may play an im portant role in the process of the membrane insertion of ApoH. (C) 2000 Els evier Science B.V. All rights reserved.