PMID:17994765
| Citation |
Becker, D, Fendler, K, Altendorf, K and Greie, JC (2007) The conserved dipole in transmembrane helix 5 of KdpB in the Escherichia coli KdpFABC P-type ATPase is crucial for coupling and the electrogenic K+-translocation step.Biochemistry 46:13920-8 |
|---|---|
| Abstract |
The KdpFABC complex of Escherichia coli, a high-affinity K+-uptake system, belongs to the group of P-type ATPases and is responsible for ATP-driven K+ uptake in the case of K+ limitation. Sequence alignments identified two conserved charged residues, D583 and K586, which are located at the center of transmembrane helix 5 (TM 5) of the catalytic KdpB subunit, and which are supposed to establish a dipole involved in energy coupling. Cells in which the two charges were eliminated or inverted by mutagenesis displayed a clearly slower growth rate with respect to wild-type cells under K+-limiting conditions. Purified KdpFABC complexes from several K586 mutants and a D583K:K586D double mutant showed a reduced K+-stimulated ATPase activity together with an increased resistance to orthovanadate. Upon reconstitution into liposomes, only the conservative K586R mutant was able to facilitate K+ transport, whereas the elimination of the positive charge at position 586 as well as inverting the charges at positions 583 and 586 (D583K:K586D) led to an uncoupling of ATP hydrolysis and K+ transport. Electrophysiological measurements with KdpFABC-containing proteoliposomes adsorbed to planar lipid bilayers revealed that in case of the D583K:K586D double mutant the characteristic K+-independent electrogenic step within the reaction cycle is lacking, thereby clearly arguing for an exact positioning of the dipole for coupling within the functional enzyme complex. In addition, these findings strongly suggest that the dipole residues in KdpB are not directly responsible for the characteristic electrogenic reaction step of KdpFABC, which most likely occurs within the K+-translocating KdpA subunit. |
| Links |
PubMed Online version:10.1021/bi701394h |
| Keywords |
Adenosine Triphosphatases; Cation Transport Proteins; Escherichia coli; Escherichia coli Proteins; Genetic Complementation Test; Ion Transport; Plasmids; Potassium; Substrate Specificity |
| edit table |
Main Points of the Paper
Please summarize the main points of the paper.
Materials and Methods Used
Please list the materials and methods used in this paper (strains, plasmids, antibodies, etc).
Phenotype Annotations
See Help:AnnotationTable for details on how to edit this table.
<protect>
| Species | Taxon ID | Strain | Gene (if known) | OMP | Phenotype | Details | Evidence | Notes |
|---|---|---|---|---|---|---|---|---|
|
Escherichia coli |
kdpA |
reduced affinity for substrate- K+ |
Other |
transport assay |
Binding Assay |
Table 1 | ||
|
Escherichia coli |
kdpB |
reduced affinity for substrate- K+ |
Other |
transport assay |
Binding Assay |
Table 1 | ||
|
Escherichia coli |
kdpC |
reduced affinity for substrate- K+ |
Other |
transport assay |
Binding Assay |
Table 1 | ||
|
Escherichia coli |
kdpA |
reduced affinity for substrate- Rb+ |
Other |
transport assay |
Binding Assay |
Table 1 | ||
|
Escherichia coli |
kdpA |
increased affinity for substrate- Rb+ |
Other |
transport assay |
Binding Assay |
Table 1 | ||
|
Escherichia coli |
kdpA |
reduced discrimination between substrates |
Other |
transport assay |
Binding Assay |
Table 1 | ||
| edit table |
</protect>
Notes
References
See Help:References for how to manage references in omp dev.
