The (Na+ + K+)-activated ATPase Enzymatic and transport properties

Modification of the E1ATP binding site of Na+/K+‐ATPase by the chromium complex of adenosine 5′‐[β,γ‐methylene]triphosphate blocks the overall reaction but not the partial activities of the E2 conformation

“…Interaction of ATP and Na+ with the E,ATP site have been reported to stimulate K' -activated p-nitrophenylphosphatase . This phenomenon has been interpreted as stimulation of the K+-phosphatase activity by the formation of a phosphointermediate [33]. The conformational nature of this putative phosphointermediate is unknown.…”

The receptor function of the Na+, K+-activated adenosine triphosphatase system

“…Taken together, such experiments suggest that both the pump and the receptor functions are properties of the a-subunit. Quantitative binding studies reveal that the receptor site, the phosphorylation site and the ATP-binding site (Munson, 1981(Munson, , 1983Rempeters & Schoner, 1981;Ponzio et al, 1983;Bobis et al, 1983) are present in a 1:1:1 ratio on the active Na,K-ATPase molecule (Wallick et al, 1979;Robinson & Flashner, 1979;Sweadner & Goldin, 1980;Cantley, 1981;Schuurmans Stekhoven & Bonting, 1981;J0rgensen, 1982) (Stein, 1979;Repke & Dittrich, 1979) or (ii) one permanent-high-affinity ATP binding site and one permanent low-affinity, regulatory, ATP binding site per two associated a-subunits (Robinson, 1980;Fritzsch & Koepsell, 1983) or (iii) only a single a-subunit monomer containing one ATP site with changing affinity during the turnover cycle and one cardiac glycoside receptor site (Kyte, 1981;Moczydlowski & Fortes, 1981;Peters et al, 1981) is a much discussed question. These three possibilities are shown schematically in Fig.…”

“…The cell surface Na,K-ATPase is one of the most versatile membrane systems as it combines receptor function, coupled Na+: K+ transport and ATPase activity in a single molecule composed of only two different polypeptide chains (a and P) and lipids (Wallick et al, 1979;Robinson & Flashner, 1979;Sweadner & Goldin, 1980;Cantley, 1981;Schuurmans Stekhoven & Bonting, 1981;J0rgen-sen, 1982), as outlined schematically in Fig. 1.…”

Insulin or sulfonylurea treatments of the diabetics differentially affect erythrocyte membrane and serum enzymes and extent of protein glycosylation

“…In parallel studies v~ found that the phospholipid composition of the erythrocyte membrances had altered significantly in all the experimental groups (Dave, I~ R and Katyam, S.S. upublished observations). It would therefore appear that the observed decrease in the Na*,K*-ATPa~ ac6vity may be atlfibuted e~er to al~dute decreese in the content of the enzyme units and/or to altered mentrame ph~0t~ipid ~u (23).…”