(Na + + K + ) ATPase has one functioning phosphorylation site per α subunit

• Published in: Nature (London) 1981-03, Vol.290 (5804), p.338-339
• Main Authors: Peters, W. H. M, Swarts, H. G. P, de Pont, J. J. H. H. M, Stekhoven, F. M. A. H. Schuurmans, Bonting, S. L
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - metabolism; Animals; Binding Sites; Humanities and Social Sciences; Kidney - enzymology; letter; Macromolecular Substances; multidisciplinary; Phosphorylation; Protein Conformation; Rabbits; Science; Science (multidisciplinary); Sodium-Potassium-Exchanging ATPase - metabolism
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/290338a0

(Na + + K + )ATPase contains two different subunits, a catalytic subunit ( α ) and a subunit with uncertain function (β). The enzyme binds ATP, ouabain and vanadate, and can be phos-phorylated by ATP as well as by inorganic phosphate. From the previously reported maximal binding and phosphorylation capacities of 3.5–4.3 nmol P per mg protein 1–3 (based on Lowry protein determination) and the earlier molecular weight value of ∼250,000 1,2 , a molar binding and phosphorylation capacity of 0.87–1.07 mol per mol enzyme was derived. As it is generally agreed that the enzyme molecule contains two α subunits 1–6 or even a multiple of two 7,8 , it has been suggested that the enzyme operates by means of a so-called ‘half-of-the-sites mechanism’, whereby only one of the two α subunits can be phosphorylated at any one time 9,10 . We now present evidence that every α subunit can be phosphorylated simultaneously, which rules out the operation of such a mechanism.