[Properties of lipid bilayer membranes modified by brain Na+,K+-ATPase subunits]

Large (alpha) and small (beta) subunits (SU) of the enzyme were obtained from the high-purified Na+, K+-ATPase preparations of the cattle brain. Molecular masses of the subunits (95 and 55 kD, respectively) have been determined and the properties of bilayer lipid membranes (BLM) modified by them were investigated. The both proteins are capable of inducing the channel conductivity in BLM which is selective to alkaline metals ions in case of alpha-SU, alpha-SUE modified BLM possess some properties of Na+, K+-ATPase: the cardial glucosides at large and small doses have a specific action, the action of the above glycosides and vanadate differs; vanadate intensifies the inhibitory effect of ouabain; the cardial glycosides and K+ have an antagonistic action; the effect of ouabain depends on the content of Ca2+ in the medium. At the same time other properties of this enzyme (dependence on ATP, magnesium ions, etc.) are not manifested with introduction into BLM. It is supposed that the ability of Na+, K+- ATPase subunits to form channel-like current fluctuations in BLM is a property of the obtained proteins and it is not obligatory realized in the processes of active K+ and Na+ transmembrane transfer.