Molecular cloning and functional expression in bacteria of the potassium transporters CnHAK1 and CnHAK2 of the seagrass Cymodocea nodosa

Molecular cloning and functional expression in bacteria of the potassium transporters CnHAK1 and... The cDNAs CnHAK1 and CnHAK2, encoding K+ transporters, were amplified from the leaves of the seagrass Cymodocea nodosa. None of these transporters suppressed the K+ deficiency of a Saccharomyces cerevisiae mutant, but both suppressed the equivalent defect of an Escherichia coli mutant. Overexpression of the transporter CnHAK1, but not CnHAK2, mediated very rapid K+ or Rb+ influxes in the E. coli mutant. The concentration dependence of these influxes demonstrated that CnHAK1 is a low-affinity K+ transporter, which does not discriminate between K+ and Rb+. CnHAK1 expressed in E. coli worked in reverse when the external K+ concentrations were low, and we established the condition of a simple functional test of K+ loss for transporters of the Kup-HAK family. In comparison with its homologue barley transporter HvHAK2, CnHAK1 was insensitive to Na+. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Molecular Biology Springer Journals

Molecular cloning and functional expression in bacteria of the potassium transporters CnHAK1 and CnHAK2 of the seagrass Cymodocea nodosa

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Publisher
Kluwer Academic Publishers
Copyright
Copyright © 2002 by Kluwer Academic Publishers
Subject
Life Sciences; Biochemistry, general; Plant Sciences; Plant Pathology
ISSN
0167-4412
eISSN
1573-5028
D.O.I.
10.1023/A:1019951023362
Publisher site
See Article on Publisher Site

Abstract

The cDNAs CnHAK1 and CnHAK2, encoding K+ transporters, were amplified from the leaves of the seagrass Cymodocea nodosa. None of these transporters suppressed the K+ deficiency of a Saccharomyces cerevisiae mutant, but both suppressed the equivalent defect of an Escherichia coli mutant. Overexpression of the transporter CnHAK1, but not CnHAK2, mediated very rapid K+ or Rb+ influxes in the E. coli mutant. The concentration dependence of these influxes demonstrated that CnHAK1 is a low-affinity K+ transporter, which does not discriminate between K+ and Rb+. CnHAK1 expressed in E. coli worked in reverse when the external K+ concentrations were low, and we established the condition of a simple functional test of K+ loss for transporters of the Kup-HAK family. In comparison with its homologue barley transporter HvHAK2, CnHAK1 was insensitive to Na+.

Journal

Plant Molecular BiologySpringer Journals

Published: Oct 13, 2004

References

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