The Nha1 antiporter from the Saccharomyces cerevisiae is an extremely stable plasma membrane protein.
Hana Flegelova (1), Rosine Haguenauer-Tsapis (2), Hana Sychrova (1)
(1) Dpt. of Membrane Transport, Institute of Physiology, Videnska 1083, Prague 4, 142 20, Czech Republic; (2) Institut Jacques Monod-CNRS, Universites Paris VI and VII, 2 place Jussieu, 75251 PARIS Cedex 05, France
Na + /H + antiporters are membrane proteins that exchange alkali metal cations to protons. In bacteria, lower eukaryots and plants, they are especially important for the maintenance of cell tolerance to high concentration of alkali metal cations in the environment. Nha1 antiporter from S. cerevisiae is localized in the plasma membrane and mediates the efflux of alkali metal cations out of the cell. Except the role in the protection of cells from toxic alkali metal cations, it also plays a role in regulation of intracellular pH, cell volume and response to the osmotic stress. In this work, we studied the stability of Nha1p in various stress conditions. We have found that several conditions in which other membrane proteins (e.g. Fur4p or Gal2p) are rapidly internalized and degraded do not affect localization of Nha1 protein. Only two stress conditions (high pH and high temperature) caused the internalization and degradation of Nha1p. Our results indicate that Nha1 antiporter is an important protein for the cell physiology and it is therefore stably localized to the plasma membrane. The work was supported with grants GA AS CR IAA5011407 and AVOZ 50110509.