PROTEIN ATTRACTION IN MEMBRANES INDUCED BY LIPID FLUCTUATIONS

The nonspecific lipid-mediated attraction between two proteins embedde d in a bilayer membrane have been investigated for a model system usin g Monte Carlo simulations. We found two types of attraction with diffe rent regimes. A depletion-induced attraction in the range r < sigma(L) , where sigma(L) is the diameter of a lipid and r is the distance betw een the surfaces of the two proteins, and a fluctuation-induced attrac tion in the range 1 < r/sigma(L) < 6, which originates from the gradie nts of density and orientational fluctuations of the lipids around eac h protein. The effective potential of the latter type of attraction de cays exponentially with U(r) similar to exp(r/xi) where the correlatio n length is xi/sigma(L) approximate to 3.2 in the present model system .