Open AccessEvidence for a Mg 2+ ‐Induced Conformational Change at the ATP‐Binding Site of (Na + + K + )‐ATPase Demonstrated with a Photoreactive ATP‐Analogue
Author(s) -
REMPETERS Gerold,
SCHONER Wilhelm
Publication year - 1981
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1981.tb06441.x
Subject(s) - atpase , chemistry , conformational change , binding site , crystallography , biophysics , stereochemistry , enzyme , biochemistry , biology
1 The 3′‐ribosyl ester of ATP with 2‐nitro‐4‐azidophenyl propionic acid has been prepared and its ability to act, as a photoaffinity label of (Na + + K + )‐ATPase has been tested. 2 In the dark 3′‐O‐[3‐(2‐nitro‐4‐azidophenyl)‐propionyl]adenosine triphosphate (N 3 ‐ATP) is a substrate of (Na + + K + )‐ATPase and a competitive inhibitor of ATP hydrolysis. 3 Upon irradiation by ultraviolet light, N 3 ‐ATP photolabels the high‐affinity ATP‐binding site and is covalently attached to the α‐subunit and an approximately 12000‐M r component. 4 Photolabeling of the α‐subunit by N 3 ‐ATP irreversibly inactivates (Na + + K + )‐ATPase. 5 Photoinactivation is strictly Mg 2+ ‐dependent. Na + enhances the inactivation. ATP or ADP and K+ protect the enzyme against inactivation. 6 Mg 2+ ;, in concentrations required for photoinactivation, protects (Na + + K + )‐ATPase against inactivation by tryptic digestion under controlled conditions. 7 It is assumed that a conformational change of the ATP‐binding site of (Na + +K + )‐ATPase occurs upon binding of Mg 2+ to a low‐affinity site.