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 />
protein-protein interactions between mcp units inside the phage coat, which are essential<br />
in providing stability to the particle. Finally, the C-terminus <strong>of</strong> mcp (residues 40-50) is<br />
enriched in positively charged lysines. This domain lines the inside <strong>of</strong> the phage particle<br />
and is responsible by non-specific interactions <strong>with</strong> DNA. The amino acid sequence <strong>of</strong><br />
mcp and the structure <strong>of</strong> the <strong>membrane</strong> bound form is shown in Figure II-2.<br />
The N-terminus <strong>of</strong> the <strong>membrane</strong> bound form <strong>of</strong> mcp is a flexible α-helix <strong>with</strong><br />
amphipatic character. A loop connects this amphipatic domain <strong>with</strong> the trans<strong>membrane</strong><br />
helix (Figure II-2). The trans<strong>membrane</strong> domain <strong>of</strong> mcp is tilted by 20 ± 10º <strong>with</strong> respect<br />
to the lipid bilayer normal (Glaubitz et al., 2000; Koehorst et al., 2004). ESR and<br />
fluorescence <strong>studies</strong> making use <strong>of</strong> site-directed labelling <strong>of</strong> mcp (Spruijt et al., 1996;<br />
Stopar et al., 1997a) allowed to conclude that Thr 36 is located in the center <strong>of</strong> the bilayer<br />
in DOPC and 1,2-dioleoyl-sn-glycerol-3-phosphatidylglycerol (DOPG) bilayers, while<br />
aminoacids 25 and 46 delineate the edges <strong>of</strong> the trans<strong>membrane</strong> domain <strong>of</strong> mcp. DOPC<br />
is expected to present ideal hydrophobic matching conditions to mcp.<br />
A<br />
B<br />
Figure II-2: A - Amino acid sequence <strong>of</strong> mcp (taken from Hemminga et al., 1992). B – Structure <strong>of</strong><br />
the <strong>membrane</strong> bound form <strong>of</strong> mcp (taken from Stopar et al., 2003).<br />
mcp was also found to be strongly anchored to the lipid bilayer through its C-<br />
terminus, namely by the two phenylalanines found there and by three lysine residues.<br />
When mcp was incorporated in bilayers <strong>with</strong> slightly thinner or thicker hydrophobic<br />
49