Purification from a total cellular lysate of a protein modifying the sensitivity of Na+/K+ ATPase to ouabain]

A protein (32,000 dalton) has been purified from M2FS cells derived from the murine plasmocytoma MOPC 173. Like tropomyosin, this protein when added with Ca++ to EDTA-treated plasma membranes prepared from the same cell, induced a drastic increase in the Na+/K+ atpase resistance to ouabain.