| Autor: |
Darley CP; Department of Developmental Genetics, Vrije Universiteit, BioCentrum Amsterdam, De Boelelaan 1087, Amsterdam, 1081 HV, The Netherlands., van Wuytswinkel OC, van der Woude K, Mager WH, de Boer AH |
| Jazyk: |
angličtina |
| Zdroj: |
The Biochemical journal [Biochem J] 2000 Oct 01; Vol. 351 (Pt 1), pp. 241-9. |
| DOI: |
10.1042/0264-6021:3510241 |
| Abstrakt: |
Sodium at high millimolar levels in the cytoplasm is toxic to plant and yeast cells. Sequestration of Na(+) ions into the vacuole is one mechanism to confer Na(+)-tolerance on these organisms. In the present study we provide direct evidence that the Arabidopsis thaliana At-NHX1 gene and the yeast NHX1 gene encode low-affinity electroneutral Na(+)/H(+) exchangers. We took advantage of the ability of heterologously expressed At-NHX1 to functionally complement the yeast nhx1-null mutant. Experiments on vacuolar vesicles isolated from yeast expressing At-NHX1 or NHX1 provided direct evidence for pH-gradient-energized Na(+) accumulation into the vacuole. A major difference between NHX1 and At-NHX1 is the presence of a cleavable N-terminal signal peptide (SP) in the former gene. Fusion of the SP to At-NHX1 resulted in an increase in the magnitude of Na(+)/H(+) exchange, indicating a role for the SP in protein targeting or regulation. Another distinguishing feature between the plant and yeast antiporters is their sensitivity to the diuretic compound amiloride. Whereas At-NHX1 was completely inhibited by amiloride, NHX1 activity was reduced by only 20-40%. These results show that yeast as a heterologous expression system provides a convenient model to analyse structural and regulatory features of plant Na(+)/H(+) antiporters. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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