title: The dynamics of the cell membrane coupling of the reaction of the Na, K-ATPase with ATP to the reaction with the cations.
abstract: From a functional point of view the dynamics of the cell membrane is perhaps most clearly expressed in the existence in the membrane of elements which can convert chemical bond energy into transport of cations against electrochemical gradients, i.e. elements which act as chemi-osmotic transducers. An example is the Na, K-ATPase which by hydrolysis of ATP transport Na+ out and K+ into the cell against their gradients. With Na+ the system exists in a Na+ -form with high Na+, low K+ and high ATP affinity while with K+ it exists in a K+ -form with high K+, low Na+ and low ATP affinity. The Na+ -form is a deprotonated while the K+-form is a protonated form, i.e. there is a Bohr-effect on the Na+ relative to K+ affinity. ATP has a deprotonating effect while phosphorylation of the system by ATP has a protonating effect, i.e. ATP turns the system into the Na+-form while phosphorylation by ATP turns the system into the K+-form. The change in protonation is observed as a change in conformation suggesting that protons take part in formation of the tertiary and the quarternary structure of the system. The cation sites can thus sense the difference between Na+ and K+ and the adaptation of the site to the cation leads to a change in protonation and by this to a change in the configuration of the ATP site. And vice versa the reaction with ATP changes via a change in protonation of the system the affinity of the cation sites. The chemical reaction is thus coupled to the reaction with the cations via a change in protonation which means changes in pK values of the system.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology*; D007700:Kinetics; D011188:Potassium / Q000378:metabolism*; D011485:Protein Binding; D011732:Pyridoxal Phosphate / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D011732:Pyridoxal Phosphate; D000255:Adenosine Triphosphate; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium