Radiation inactivation of (Na + + K +)-ATPase a small target size for the K +-occluding mechanism

Abstract

Radiation inactivation of partially purified (Na + + K +)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) from pig kidney outer medulla shows that the target size for Rb + occlusion by the enzyme (in the absence of phosphorylation) is much smaller than the target size for p- nitrophenyl phosphatase activity , which is itself smaller than the reported target size for (Na + + K +)-ATPase activity.