Cargando…
Pre-steady-state charge translocation in NaK-ATPase from eel electric organ
Time-resolved measurements of charge translocation and phosphorylation kinetics during the pre-steady state of the NaK-ATPase reaction cycle are presented. NaK-ATPase-containing microsomes prepared from the electric organ of Electrophorus electricus were adsorbed to planar lipid bilayers for investi...
Formato: | Texto |
---|---|
Lenguaje: | English |
Publicado: |
The Rockefeller University Press
1993
|
Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2229170/ https://www.ncbi.nlm.nih.gov/pubmed/8270908 |
_version_ | 1782150066304188416 |
---|---|
collection | PubMed |
description | Time-resolved measurements of charge translocation and phosphorylation kinetics during the pre-steady state of the NaK-ATPase reaction cycle are presented. NaK-ATPase-containing microsomes prepared from the electric organ of Electrophorus electricus were adsorbed to planar lipid bilayers for investigation of charge translocation, while rapid acid quenching was used to study the concomitant enzymatic partial reactions involved in phosphoenzyme formation. To facilitate comparison of these data, conditions were standardized with respect to pH (6.2), ionic composition, and temperature (24 degrees C). The different phases of the current generated by the enzyme are analyzed under various conditions and compared with the kinetics of phosphoenzyme formation. The slowest time constant (tau 3(-1) approximately 8 s-1) is related to the influence of the capacitive coupling of the adsorbed membrane fragments on the electrical signal. The relaxation time associated with the decaying phase of the electrical signal (tau 2(-1) = 10-70 s-1) depends on ATP and caged ATP concentration. It is assigned to the ATP and caged ATP binding and exchange reaction. A kinetic model is proposed that explains the behavior of the relaxation time at different ATP and caged ATP concentrations. Control measurements with the rapid mixing technique confirm this assignment. The rising phase of the electrical signal was analyzed with a kinetic model based on a condensed Albers-Post cycle. Together with kinetic information obtained from rapid mixing studies, the analysis suggests that electroneutral ATP release, ATP and caged ATP binding, and exchange and phosphorylation are followed by a fast electrogenic E1P-->E2P transition. At 24 degrees C and pH 6.2, the rate constant for the E1P-- >E2P transition in NaK-ATPase from eel electric organ is > or = 1,000 s- 1. |
format | Text |
id | pubmed-2229170 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 1993 |
publisher | The Rockefeller University Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-22291702008-04-23 Pre-steady-state charge translocation in NaK-ATPase from eel electric organ J Gen Physiol Articles Time-resolved measurements of charge translocation and phosphorylation kinetics during the pre-steady state of the NaK-ATPase reaction cycle are presented. NaK-ATPase-containing microsomes prepared from the electric organ of Electrophorus electricus were adsorbed to planar lipid bilayers for investigation of charge translocation, while rapid acid quenching was used to study the concomitant enzymatic partial reactions involved in phosphoenzyme formation. To facilitate comparison of these data, conditions were standardized with respect to pH (6.2), ionic composition, and temperature (24 degrees C). The different phases of the current generated by the enzyme are analyzed under various conditions and compared with the kinetics of phosphoenzyme formation. The slowest time constant (tau 3(-1) approximately 8 s-1) is related to the influence of the capacitive coupling of the adsorbed membrane fragments on the electrical signal. The relaxation time associated with the decaying phase of the electrical signal (tau 2(-1) = 10-70 s-1) depends on ATP and caged ATP concentration. It is assigned to the ATP and caged ATP binding and exchange reaction. A kinetic model is proposed that explains the behavior of the relaxation time at different ATP and caged ATP concentrations. Control measurements with the rapid mixing technique confirm this assignment. The rising phase of the electrical signal was analyzed with a kinetic model based on a condensed Albers-Post cycle. Together with kinetic information obtained from rapid mixing studies, the analysis suggests that electroneutral ATP release, ATP and caged ATP binding, and exchange and phosphorylation are followed by a fast electrogenic E1P-->E2P transition. At 24 degrees C and pH 6.2, the rate constant for the E1P-- >E2P transition in NaK-ATPase from eel electric organ is > or = 1,000 s- 1. The Rockefeller University Press 1993-10-01 /pmc/articles/PMC2229170/ /pubmed/8270908 Text en This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/). |
spellingShingle | Articles Pre-steady-state charge translocation in NaK-ATPase from eel electric organ |
title | Pre-steady-state charge translocation in NaK-ATPase from eel electric organ |
title_full | Pre-steady-state charge translocation in NaK-ATPase from eel electric organ |
title_fullStr | Pre-steady-state charge translocation in NaK-ATPase from eel electric organ |
title_full_unstemmed | Pre-steady-state charge translocation in NaK-ATPase from eel electric organ |
title_short | Pre-steady-state charge translocation in NaK-ATPase from eel electric organ |
title_sort | pre-steady-state charge translocation in nak-atpase from eel electric organ |
topic | Articles |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2229170/ https://www.ncbi.nlm.nih.gov/pubmed/8270908 |