[Inactivation of rat brain Na+ K+ ATPase by sodium dodecylsulfate: effect of pH, magnesium ions and temperature].

The relative stabilities to SDS inactivation of the rat brain Na(+)-ATPase catalytic subunit isoforms in the conditions of the surface charge modulation and temperature modification of the physical state of the membrane lipids were examined. The higher sensitivity of the Na+,K(+)-ATPase a1-isoform than a+ to SDS inactivation occurs under the conditions of the detergent treatment of microsomes at pH 7.5 and room temperature. The decrease in pH in ATP-free medium up to 6.2 or temperature elevation up to 37 degrees C eliminates the differences in SDS sensitivity of the Na+,K(+)-ATPase isoforms. The enhancement of the SDS binding with a subunit due to changes in membrane surface charge in the first case or increase of accessibility of the protein intramembrane regions for detergent due to the decrease of the packing density of the boundary lipids in the second case are supposed.