What is of particular interest (to drug discovery), based on their structural similarities [185 188], is the increasing recognition [149,189 199] (Fig. 3) that pharmaceutical drugs also get into and out of cells by 'hitchhiking' on such transporters, and not – to any significant extent – by passing through phospholipid bilayer portions of cellular membranes.
Increased DMPC content was found to slow down the formation of a partially folded intermediate, which is ascribed to increased bending rigidity of the bilayer portion.
Furthermore, our accessibility data indicate that the ends of the S6 helices appear to splay into the lower portion of the bilayer.
Both electron density profiles and reciprocal space modeling indicate that (1) the incorporation of up to 30 mol % GM1 into EPC bilayers has little effect on bilayer organization and (2) the oligosaccharide portion of the GM1 molecule extends at least 12 A beyond the EPC head group into the fluid space, implying that the GM1 head group is nearly fully extended from the bilayer surface.
Lipid-soluble, nonpolar molecules pass readily through the membrane because they dissolve in the hydrophobic, nonpolar portion of the lipid bilayer.
At this an argument exists that the bilayer formation is still energetically unfavorable as the hydrophobic portion of the molecules is still in contact with water.
The hydrophobic portion of the helix partially penetrates the bilayer, thus conferring membrane curvature generation and sensing properties to the protein (Itoh et al., 2001; Ford et al., 2002).
One caveat of this analysis is that it does not take into account any portion of the globular oligomer that may be inserted into the bilayer.
Solvent paramagnetic relaxation enhancement analyses showed that the bilayer thickness around the HCV ion channel is substantially smaller than expected, and thus a significant portion of the previously assigned membrane-embedded region is solvent exposed.
Fujiyoshi et al (1994) have proposed that the inner portion of the envelope reflects a matrix protein lipid composite, rather than a classical phospholipid bilayer leaflet with associated protein.
