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Biophysical studies of membrane proteins/peptides. Interaction with ...

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INTRODUCTION: LIPID-PROTEIN INTERACTIONS<br />

Figure I.22 - Schematic representation <strong>of</strong> protein-protein interactions mediated by hydrophobic<br />

mismatch. (a) – Hydrophobically matched <strong>membrane</strong>. (b, c) - Lipid-mediated protein-protein attraction by<br />

same type <strong>of</strong> hydrophobic mismatch. (d) - Lipid-mediated protein-protein repulsion by opposite type <strong>of</strong><br />

hydrophobic mismatch (Taken from Gil et al., 1998).<br />

When more than one lipid species is present, wetting <strong>of</strong> <strong>membrane</strong> <strong>proteins</strong> also<br />

implies formation <strong>of</strong> an interface between lipids in the wetting phase and lipids in the<br />

protein-poor phase. Again the tendency to minimize the interface between these two<br />

phases can lead to coalescence or capillary condensation <strong>of</strong> wetting domains and<br />

stimulation <strong>of</strong> protein-protein interactions (Fig. I.21.c)). In this way, wetting occurs in<br />

addition to direct protein-protein (Van der Waals and electrostatic) and the above<br />

described lipid-mediated interactions, by selecting the environment in which they take<br />

place, i.e., wetting provides the mechanism for modulation <strong>of</strong> <strong>membrane</strong> protein<br />

organization (clustering and aggregation) on larger length scales (Gil et al., 1998).<br />

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