Protein-Membrane Interactions in the Complex Biological Milieu
Alterations in the lipid composition of biological membranes can have dramatic effects on their ability to interact with soluble proteins. In a series of studies employing large unilamellar vesicles (LUVs) produced by an extrusion technique, we have characterized the influence of membrane components on protein-membrane interactions. Much of our understanding of how and why proteins interact with seemingly inert membrane surfaces stems mainly from studies involving one or two protein component systems. These studies, however, do not accurately reflect the interactions that occur in the complex biological milieu (reviewed by Horbett and Brash, 1987). There have been very few studies reported on the interactions of proteins with liposomal systems incubated with whole blood. There are two main reasons for this. First, the large majority of studies on the association of plasma proteins with liposomes in vitro have been performed employing multilamellar systems. Due to the variable lamellarity of liposomes of different lipid compositions, quantification of the amount of various proteins associated per liposome has not been possible. Second, convenient techniques have not been available for the isolation of liposomes, particularly LUVs, from blood components. We have recently described a rapid method for the isolation of well-defined large unilamellar liposomes from the blood of liposome-treated mice (Chonn et al., 1991). With such a procedure now available, we have started to biochemically and immunologically characterize the amount and type of proteins associated with liposomes exposed to the complex biological milieu.
KeywordsCholesterol Albumin Carbohydrate Electrophoresis Macromolecule
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