| Autor: |
Toshio Yamaguchi, James C., Apse, Maris P., Huazhong Shi, Blumwald, Eduardo |
| Předmět: |
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| Zdroj: |
Proceedings of the National Academy of Sciences of the United States of America; 10/14/2003, Vol. 100 Issue 21, p12510-12515, 6p |
| Abstrakt: |
We conducted an analysis of the topology of AtNHX1, an Arabidopsis thaliana vacuolar Na[SUP+]/H[SUP+] antiporter. Several hydrophilic regions of the antiporter were tagged with a hemagglutinin epitope, and protease protection assays were conducted to determine the membrane topology of the antiporter by using yeast as a heterologous expression system. The overall structure of AtNHX1 is distinct from the human Na[SUP+]/H[SUP+] antiporter NHE1 or any known Na[SUP+]/H[SUP+] antiporter. It is comprised of nine transmembrane domains and a hydrophilic C-terminal domain. Three hydrophobic regions do not appear to span the tonoplast membrane, yet appear to be membrane associated. Our results also indicate that, whereas the N terminus of AtNHX1 is facing the cytosol, almost the entire C-terminal hydrophilic region resides in the vacuolar lumen. Deletion of the hydrophilic C terminus resulted in a dramatic increase in the relative rate of Na[SUP+]/H[SUP+] transport. The ratio of Na[SUP+]/K[SUP+] transport was twice that of the unmodified AtNHX1. This altered ratio resulted from a relatively small decrease in K[SUP+]/H[SUP+] transport with a large increase in Na[SUP+]/H[SUP+] transport. The vacuolar Iocalization of the C terminus of the AtNHX1, taken together with the regulation of the antiporter selectivity by its C terminus, demonstrates the existence of luminal vacuolar regulatory mechanisms of the antiporter activity. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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