title: The molecular size required varies according to the reaction step round the sodium pump cycle.
abstract: Progress along the path of the sodium pump cycle requires a stepwise recruitment of additional subunits for maximal activity. These results show that whereas a particle the size of the alpha beta protomer presents Na+,K+-ATPase activity at 10 microM ATP, an additional subunit, perhaps a second alpha-chain, is required to obtain the much greater Na+,K+-ATPase activity resulting from the occupation of low-affinity ATP sites at physiological ATP concentrations. A non-phosphorylating ATP analogue, however, will modestly stimulate the Na+,K+-ATPase activity acting at an alternative low-affinity site or step on the alpha beta protomer.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology; D000818:Animals; D007473:Ion Channels / Q000378:metabolism*; D007668:Kidney / Q000201:enzymology; D046911:Macromolecular Substances; D008970:Molecular Weight; D010766:Phosphorylation; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism* / Q000528:radiation effects; D013552:Swine
chemical_list: D007473:Ion Channels; D046911:Macromolecular Substances; D000266:Adenylyl Imidodiphosphate; D000255:Adenosine Triphosphate; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase