Subunit Distribution of Sulfhydryl Groups and Disulfide Bonds in Renal Na,K-ATPase

Abstract

Sulfhydryl groups and disulfide bonds have been suggested to have essential roles in Na, K-ATPase. This chapter discusses the subunit distribution of these two kinds of groups on a purified Na, K-ATPase. Purified Na, K-ATPase was obtained from dog kidney by the method of Jørgensen. The number of disulfide bonds was determined from the difference in quantity of sulfhydryl groups titrated before and after reduction of the enzyme. The distribution of the 14C label over the subunits of Na, K-ATPase after treatment with [14C]NEM was determined by Sepharose CL-4B column chromatography. The number of sulfhydryl groups in each subunit was calculated from the percentage in each fraction of total radioactivity recovered from the column of Sepharose 4B. From the data obtained in the chapter, it can be concluded that there were eight disulfide bonds in the unit of Na, K-ATPase. The number of disulfide bonds in each subunit calculated was based on the distribution of radioactivity.