Role of β- and α-Structures of Membrane Proteins in Plasmalemma Structure Change.

Changes in the structure of plasma membranes affect functions of membranes and cells. Some of these changes could lead to the development of pathologies in an organism, which makes it important to study effects of the changes in the structure of membranes on their functions. It is considered established at present that when stress hormones and androgens interact with plasma membranes, their structure changes. In the process, interactions between proteins and lipids change in plasmalemmas, and a rigid quasi-periodic network of protein-lipid domains associated with cytoskeleton is formed. Initiators of formation of protein-lipid domains are membrane proteins, which change their secondary structure during interaction of the membrane with hormones. However, it is still unclear exactly what changes in the secondary structure of membrane proteins contribute to formation of the protein-lipid domains around them. The aim of this work was to identify these secondary structures in membrane proteins. To achieve this goal, changes in the structure of membranes during their interaction with dehydroepiandrosterone, cortisol, androsterone, testosterone, and adrenaline were studied. In this work, a fluorescent method for measuring relative microviscosity of membranes using pyrene probe was used to study changes in the membrane structure. Change in the secondary structure of membrane proteins during structural transitions in the membranes was studied by measuring IR absorption spectra of the membranes. It has been established that initiators of the emergence of protein-lipid domains in the plasma membranes are membrane proteins, in which, proportion of the β-structures increases after interaction with hormones. At the same time, appearance of new α-helices in the membrane proteins does not enhance affinity between the membrane proteins, and protein-lipid domains are not formed. On the contrary, appearance of a large number of α-helices in the membrane proteins could lead to the decrease in microviscosity of the lipid bilayer.