Low-affinity potassium uptake system in Bacillus acidocaldarius.
AUTOR(ES)
Michels, M
RESUMO
Cells of Bacillus acidocaldarius that were grown with 2.7 mM K+ expressed a low-affinity K+ uptake system. The following observations indicate that its properties closely resemble those of the Escherichia coli Trk and Streptococcus faecalis KtrI systems: (i) the B. acidocaldarius system took up K+ with a Km of 1 mM; (ii) it accepted Rb+ (Km of 6 mM; same Vmax as for K+); (iii) it was still active in the presence of low concentrations of sodium; (iv) the observed accumulation ratio of K+ maintained by metabolizing cells was consistent with K+ being taken up via a K+-H+ symporter; and (v) K+ uptake did not occur in cells in which the ATP level was low. Under the latter conditions, the cells still took up methylammonium ions via a system that was derepressed by growth with low levels of ammonium ions, indicating that in the acidophile ammonium (methylammonium) uptake requires a high transmembrane proton motive force rather than ATP.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=213749Documentos Relacionados
- Low-affinity potassium uptake system in the archaeon Methanobacterium thermoautotrophicum: overproduction of a 31-kilodalton membrane protein during growth on low-potassium medium.
- TRK2 is not a low-affinity potassium transporter in Saccharomyces cerevisiae.
- Evidence that a low-affinity sucrose phosphotransferase activity in Streptococcus mutans GS-5 is a high-affinity trehalose uptake system.
- Proline transport in Staphylococcus aureus: a high-affinity system and a low-affinity system involved in osmoregulation.
- Divalent Cation Block of Inward Currents and Low-Affinity K+ Uptake in Saccharomyces cerevisiae