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

In Figure I.21, theoretical simulations are shown that predict the wetting
phenomenon. For Figure I.21c), sharing of a wetting layer by two or more proteins can
give rise to colocalization and aggregation phenomena as described in detail on Section
2.11.
A B B
Figure I.21 – Computer simulation snapshots of a large protein embedded in a binary lipid matrix in
which one of the lipids is preferentially bound to the protein. (a) – Selective binding of one of the lipid
species at the protein-lipid interface. (b) – Wetting of one of the lipids around the protein. (c) – Wetting
and formation of a capillary condensate between two adjacent proteins (taken from Gil et al., 1998).
These types of lateral structures initiated by proteins can function in biomembranes
as the signal for recruitment of other molecules to those domains. This has been
proposed as the molecular mechanism behind some signalling platforms (Pérez-Gil et
al., 2005).
2.11. Lipid-mediation of protein-protein
interactions
The principle of hydrophobic matching, and the possibility of membrane proteins to
change the lipid environment around them, offer membranes a mechanism for lipidmediation
of protein-protein interactions.
When proteins change the order parameter of lipids around them, overlap of
disturbed lipids can again lead to colocalization of proteins in the same area of the
membrane or aggregation (Gil et al., 1998) (Figure I.22). The system, when moving to
equilibrium, will have the tendency to decrease the extent of presented interface, and
this is achievable by clustering of proteins and ultimately by protein aggregation. Of
course, protein aggregation can have its energetic costs that may rise from helix-dipole
moment and charge repulsion or entropic factors.
44