Purification of the Sodium- and Potassium-dependent Adenosine Triphosphatase from Canine Renal Medulla

Abstract

The (Na+ + K+) adenosine triphosphatase was obtained from canine renal medulla and partially purified. A highly active, membrane-bound enzyme was prepared from the microsomal fraction of a homogenate. The enzyme was then transferred from this particulate state to the supernatant phase by treatment with sodium deoxycholate and, in this form, it was further purified by gel filtration. The final preparation had a high specific activity which was constant over a significant region of the elution profile. When this material was examined by electrophoresis in a sodium dodecyl sulfate solvent, more than 90% of the protein was accounted for by two polypeptide chains which were present in approximately equimolar amounts. The ratio of these two polypeptides remained constant in those fractions from the gel filtration which had the highest specific activity. The protein traveled as a single component in an acetic acid-urea electrophoresis system. These results suggest that a specific complex responsible for the (Na+ + K+) adenosine triphosphatase activity has been isolated.