Saccharomyces cerevisiae cells possess an alkali metal cation antiporter encoded by the NHA1 gene. Nha1p is unique in the family of yeast Na+/H+ antiporters on account of its broad substrate specificity (Na+, Li+, K+) and its long C-terminus (56% of the whole protein). In order to study the role of the C-terminus in Nha1p function, we constructed a series of 13 truncated NHA1 versions ranging from the complete one (2958 nucleotides, 985 amino acids) down to the shortest version (1416 nucleotides, 472 amino acids), with only 41 amino acid residues after the last putative transmembrane domain. Truncated NHA1 versions were expressed in an S. cerevisiae alkali metal cation-sensitive strain (B31; ena1-4Delta nha1Delta). We found that the entire Nha1p C-terminus domain is not necessary for either the proper localization of the antiporter in the plasma membrane or the transport of all four substrates (we identified rubidium as the fourth Nha1p substrate). Partial truncation of the C-terminus of about 70 terminal amino acids improves the tolerance of cells to Na+, Li+ and Rb+ compared with cells expressing the complete Nha1p. The presence of the neighbouring part of the C-terminus (amino acids 883-928), rich in aspartate and glutamate residues, is necessary for the maintenance of maximum Nha1p activity towards sodium and lithium. In the case of potassium, the participation of the long C-terminus in the regulation of intracellular potassium content is demonstrated. We also present evidence that the Nha1p C-terminus is involved in the cell response to sudden changes in environmental osmolarity.

• MeSH
• buněčná membrána metabolismus   MeSH
• intracelulární tekutina metabolismus   MeSH
• kationty jednomocné MeSH
• koncentrace vodíkových iontů MeSH
• lithium farmakologie   MeSH
• membránové proteiny genetika   fyziologie   MeSH
• molekulární sekvence - údaje MeSH
• Na(+)-H(+) antiport genetika   fyziologie   MeSH
• osmolární koncentrace MeSH
• proteiny přenášející kationty * MeSH
• Saccharomyces cerevisiae - proteiny * MeSH
• Saccharomyces cerevisiae účinky léků   enzymologie   genetika   MeSH
• sekvence aminokyselin MeSH
• sodík MeSH
• substrátová specifita MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• kationty jednomocné MeSH
• lithium MeSH
• membránové proteiny MeSH
• Na(+)-H(+) antiport MeSH
• NHA1 protein, S cerevisiae MeSH Prohlížeč
• proteiny přenášející kationty * MeSH
• Saccharomyces cerevisiae - proteiny * MeSH
• sodík MeSH

Saccharomyces cerevisiae uses different mechanisms to adapt to changes in environmental osmolarity. Upon hyperosmotic shock, cells first mobilize a rapid rescue system that prevents excessive loss of ions and water; then in the adaptation period they accumulate a compatible solute (glycerol). When subjected to hypoosmotic shock, they rapidly release intracellular stocks of glycerol to reduce intracellular osmolarity and prevent bursting. The plasma membrane Nha1 alkali metal cation/H+ antiporter is not important in helping the cells to survive a sudden drop in external osmolarity, but is involved in the cell response to hyperosmotic shock. For this role, its long hydrophilic C-terminus is indispensable. The capacity of the Nha1 antiporter to transport potassium is regulated by Hog1 kinase. Upon sorbitol-mediated stress, the Nha1p potassium export activity decreases in order to maintain a higher intracellular concentration of solutes. The C-terminal-less Nha1 version is not inactivated and its potassium efflux activity renders cells very sensitive to hyperosmotic shock. Taken together, our results suggest an important role of Nha1p and its C-terminus in the immediate response to hyperosmotic shock as part of the rapid rescue mechanism.

• MeSH
• fyziologická adaptace fyziologie   MeSH
• iontový transport fyziologie   MeSH
• membránové proteiny genetika   metabolismus   MeSH
• mitogenem aktivované proteinkinasy genetika   metabolismus   MeSH
• Na(+)-H(+) antiport genetika   metabolismus   MeSH
• osmotický tlak MeSH
• proteiny přenášející kationty genetika   metabolismus   MeSH
• regulace genové exprese u hub fyziologie   MeSH
• Saccharomyces cerevisiae - proteiny genetika   metabolismus   MeSH
• Saccharomyces cerevisiae genetika   metabolismus   MeSH
• terciární struktura proteinů genetika   MeSH
• upregulace fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• HOG1 protein, S cerevisiae MeSH Prohlížeč
• membránové proteiny MeSH
• mitogenem aktivované proteinkinasy MeSH
• Na(+)-H(+) antiport MeSH
• NHA1 protein, S cerevisiae MeSH Prohlížeč
• proteiny přenášející kationty MeSH
• Saccharomyces cerevisiae - proteiny MeSH