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Abstract Detail


Membrane Transport

Cagnac, Olivier [1], Leterrier, Marina [1], Leon, Sebastien [2], Yeager, Mark [3], Blumwald, Eduardo [1].

Identification and characterization of a novel type of Vacuolar Na+/H+ eXchanger from S.cerevisiae : a new yeast mutant for plant gene heterologous expression.

Na+-ATPases (Ena1-4p) represents the primary pathway for Na+ exclusion in S.cerevisiae. Nha1p, the Na+/H+ plasma membrane antiporters also serve to reduce intracellular Na+. In S.cerevisiae this antiporter family includes only two other members: Nhx1p localized at the pre-vacuolar compartment level, and Kha1p describe as a K+/H+ on the golgi. All of these genes can be easily removed by gene deletion, making S.cerevisiae an ideal host for the heterologous expression and characterization of antiporters from higher eukaryotes. Contrarily to previous reports, in our experimental conditions, the vacuolar fraction extracted from different nhx1∆ yeast strain, including KTA 40-2 (ena1-4∆, nha1∆, nhx1∆, kha1∆), did not display any noticeable reduction of Na+ or K+ transport. Two other studies using different methods and yeast strain mutants, confirmed our observation. A wide functional screening of yeast mutants, from the Euroscarf collection, allowed us to identify Vnx1p, a new type of Vacuolar Na+/H+ eXchanger. Disruption of Vnx1 completely abolishes Na+ and K+/H+ exchange activity of the vacuolar fraction. Vnx1p is a low affinity transporter exhibiting a higher specificity for Na+ (apparent Km=22,43 ± 2.55 mM) than for K+ (apparent Km= 82.21 ± 16mM). Expression of the Arabidopsis gene AtNHX1 in vnx1∆ cells restore the cation transport in isolated vacuoles. This yeast mutant is a new tool that will greatly facilitate the characterization of plant antiporter using heterologous expression.


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1 - University of California, Davis, Department of Plant Sciences, One shield Ave, Mail stop 5, Plant Reproductive Biology, Extension center drive, Davis, CA, 95616-8731, USA
2 - Institut Jacques Monod, Intracellular trafficking of proteins in yeast, 2 place Jussieu, 75251 PARIS Cedex 05 (France)
3 - Scripps Clinic, Division of Cardiovascular Diseases, 10666 North Torrey Pines Road, La Jolla, CA 92037

Keywords:
yeast
cation/H+ antiporter
vacuole.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P10005
Abstract ID:379


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