Thermodynamic parameters of activation for dephosphorylation of the Na+/K+ ATPase

RM. GONZÁLEZ-LEBRERO; SB. KAUFMAN

University of Aarhus, Aarhus, Denmark

Conferencia; 12th International ATPase Conference. Na,K-ATPase and Related Transport ATPases of P-type: Structures, Mechanisms, and Roles in Health and Disease; 2008

University of Aarhus

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> The Na+/K+-ATPase couples two processes: the endergonic transport of ions and the exergonic hydrolysis of ATP, which occurs through the formation and breakdown of phosphorylated intermediates, involving an aspartyl-phosphate covalent bond [1]. As the Na+/K+-ATPase shows several exchange modes of ion transport and many of its partial reactions can be measured, including those that involve transport intermediates, it seems a very good system to study the coupling mechanism between transport and ATP hydrolysis. We show here results comparing thermodynamic parameters of activation between the hydrolysis of ATP mediated by the Na+‑ATPase (one of the possible modes of hydrolysis of ATP) with those of the dephosphorylation of denatured (unfolded) phosphoenzyme (EPdenat). Reactions were measured at temperatures ranging from 19,7 to 30,0 °C. Na+-ATPase activity took place in media containing 150 mM NaCl, 8 µM ATP ..... <!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> <!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} -->