Biophysical studies of membrane proteins/peptides. Interaction with ...
Biophysical studies of membrane proteins/peptides. Interaction with ...
Biophysical studies of membrane proteins/peptides. Interaction with ...
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PROTEIN-PROTEIN AND PROTEIN-LIPID INTERACTIONS<br />
OF M13 MCP<br />
than in vivo, as the reconstitution procedures normally result in randomized orientations<br />
for mcp instead <strong>of</strong> the single orientation observed in vivo. mcp in the <strong>membrane</strong> <strong>with</strong><br />
identical orientations are expected to present smaller protein-protein electrostatic<br />
attractive forces due to the stronger repulsion between the heavily charged C-terminus,<br />
and consequently a higher free energy is expected for the oligomeric condition. In order<br />
to achieve high local concentrations <strong>of</strong> mcp in the host <strong>membrane</strong> prior to phage<br />
assembly, a dynamic protein-lipid network should be present, characterized by absence<br />
<strong>of</strong> preferential association between coat <strong>proteins</strong> and/or lipids (Hemminga et al., 1992).<br />
Concerning the protein-lipid interactions established by mcp, it is interesting to note<br />
that the monomeric form <strong>of</strong> mcp was not able to induce sufficient immobilization <strong>of</strong> a<br />
fraction <strong>of</strong> lipid molecules so that it could be detected by ESR <strong>with</strong> spin labelled lipids<br />
(Sanders et al., 1992). On the other hand, oligomeric mcp immobilized a population <strong>of</strong><br />
lipids, especially at very high protein concentrations (Peelen et al., 1992). Thus, it can<br />
be concluded that monomeric M13 mcp is not able to induce a long living lipid<br />
boundary shell around it. Possible explanations are that the hydrophobic surface <strong>of</strong> mcp<br />
exposed to the lipids is too small or that the diffusion rate <strong>of</strong> the protein is not<br />
sufficiently lower than that <strong>of</strong> the lipids.<br />
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