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There is a large body of evidence showing that membrane proteins embedded in lipid membranes do not function alone but their activation and thus functions depend on the lipid composition surrounding them. Here we consider this issue through atomistic simulations of lipid membranes. We consider a variety of different lipid membrane domains whose composition ranges from polyunsaturated to saturated one-component lipid bilayers, and further to highly ordered many-component lipid rafts comprised of sphingolipids, cholesterol, and saturated or monounsaturated glycerophospholipids. The lipid rafts in particular are biologically very relevant since they have been found to play an important role in a variety of cellular processes such as protein sorting and programmed cell death, yet their properties are not well understood. We focus here on the lateral pressure profile which essentially describes the pressure distribution exerted by the lipids on the protein embedded in a lipid membrane. It turns out that the lateral pressure profile strongly depends on the lipid composition and is especially intriguing in raft-like membranes. Further studies of the free energy difference between active and inactive states of some membrane proteins using simplified descriptions indicates that the contribution of the lateral pressure profile in the activation can be significant. This supports the view that there is a joint interplay between lipid bilayers and membrane proteins. |