CD298 or the beta3 Na+/K+ ATPase, is a 42 kD type II transmembrane protein, also known as ATP1B3. An integral plasma membrane protein, Na+/K+ ATPase is composed of one alpha and one beta subunits. Four isoforms of the alpha and three isoforms of the beta subunits have been reported. Na+/K+ ATPase couples ATP hydrolysis to the development of an ionic gradient by pumping Na+ and K+ ions in opposite directions across the cell plasma membrane. It has broad tissue distribution, including all leukocytes and many other tissues.