SODIUM DODECYL-SULFATE SENSITIVITY OF ISOFORMS OF THE CATALYTIC SUBUNIT OF RAT-BRAIN NA-ATPASE(,K+)

Analysis of the biphasic dose-response curve of the ouabain effect on brain Na+,K+-ATPase activity revealed that the microsomal alpha(+)-iso form is more stable to inactivation by SDS than the Na+,K+-ATPase a-is oform from brain cortex and renal outer medulla of rats. Polyacrylamid e gel electrophoresis of the membrane-bound brain Na+,K+-ATPase prepar ation in the presence of SDS revealed that irreversible inactivation o f the isozymes by detergent is accompanied by their dissociation from the membrane. The alpha-isoform is more sensitive to the solubilizatio n by SDS.