APPLICATION OF PERCOLATION THEORY PRINCIPLES TO THE ANALYSIS OF INTERACTION OF ADENYLATE-CYCLASE COMPLEX PROTEINS IN CELL-MEMBRANESстатьяИсследовательская статья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:Lateral protein movement in cell membranes takes place in a medium with 'obstacles'. These obstacles are: (a) aggregates of major integral proteins immobilized by submembraneous structures and cytoskeleton, and (b) membrane lipids in the gel phase. Hormonal activation of the adenylate cyclase complex is associated with lateral mobility of the constituent proteins. Modification of the interaction of these proteins due to variation of the 'fluid' lipid fraction in reticulocyte membranes has been studied. A decrease in the percentage of 'fluid' lipids in membranes resulted in the inhibition (up to the full cessation) of the interaction of/3-adrenoreceptors with regulatory N~-proteins. The interaction of Ns-proteins with catalytic proteins stopped as well. On the oth- er hand, an increase in the 'fluid' lipid fraction led to a more intensive interaction. These facts do not arise from the functional damage of interacting proteins. Conseqently, hormonal activation of the adenylate cyclase complex depends on the fraction of 'fluid' lipids in the membrane. The data obtained are in conformity with the percolation theory which makes it possible to characterize long-distance protein movement in a medium ('fluid' lipids) containing obstacles. Thus, interacting proteins prove to diffuse within distances greatly exceed- ing protein sizes. As a consequence, the intrinsic activity of a ~-agonist, isoproterenol, varies from 1to 0 depend- ing on the 'fluid' lipid fraction. Our findings also suggest that in vitro there are no/3-receptors precoupled with N~-proteins in rat reticulocyte membranes in the absence of guanine nucleotides.