The Kdp-ATPase of Escherichia coli mediates an ATP-Dependelb, K+-independent electrogenic partial reaction
Autor(en): | Fendler, K Drose, S Epstein, W Bamberg, E Altendorf, K |
Stichwörter: | Biochemistry & Molecular Biology; CONTROL EXPRESSION; OPERON; PLASMA-MEMBRANES; POTASSIUM; PROTEINS; PUMP; SUBUNIT; TRANSPORT ATPASE | Erscheinungsdatum: | 1999 | Herausgeber: | AMER CHEMICAL SOC | Journal: | BIOCHEMISTRY | Volumen: | 38 | Ausgabe: | 6 | Startseite: | 1850 | Seitenende: | 1856 | Zusammenfassung: | Charge transport by the K+ transporting Kdp-ATPase from Escherichia coli was investigated using planar lipid membranes to which liposomes reconstituted with the enzyme were adsorbed. To study reactions in the absence of K+, given some contamination of solutions with K+, we used a mutant of Kdp whose affinity for K+ was 6 mM instead of the wild-type whose affinity is 2 mu M. Upon rapid release of ATP from caged ATP, a transient current occurred in the absence of K+. In the presence of K+, a stationary current was seen. On the basis of their structural similarity, we propose a kinetic model for the Kdp-ATPase analogous to that of the Na+K+-ATPase. In this model, the first, K+-independent step is electrogenic and corresponds to the outward transport of a negative charge. The second, K+-translocating step is probably also electrogenic and corresponds to transport of positive charge to the intracellular side of the protein. |
ISSN: | 00062960 | DOI: | 10.1021/bi982238u |
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geprüft am 23.05.2024