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

homogeneous distribution of lipids in the membrane does have an energetic entropic
cost and the degree of protein-lipid selectivity is a balance between the need to satisfy
hydrophobic matching conditions in the protein-lipid interface and the intrinsic
tendency of the system for mixing.
Figure I.18 – Illustration of a lipid bilayer with an embedded protein and two different lipid species.
The hydrophobic matching principle implies an accumulation of the lipid species that is hydrophobically
best matched to the protein (taken from Jensen and Mouritsen, 2004).
The hydrophobic surface of a membrane protein is not smooth. The interface
between the protein and the lipids surrounding it is likely to be heterogeneous, and the
interactions taking place there complex (Lee, 2003). Still the results described above,
concerning the presence of a fixed stoichiometry for annular lipids, denote some degree
of ordering in the TM alpha helix-lipid interface and in this way, processes of lipid
binding to simpler systems such as single TM domains are suitable to be described in
terms of a uniform surface for which several (12) identical binding sites are available
(Marsh et al., 2002). With total coverage of the protein surface by lipids, one lipid
molecule must leave the surface before another can enter. In this sense, the process can
be depicted as competitive binding of lipids at the binding sites on the protein surface
(Lee, 2003) (Figure I.19). This method of analysis has been applied with success to
even more complex membrane proteins (O’ Keefe et al., 2000; Williamson et al., 2002;
Powl et al., 2003).
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