The Saccharomyces cerevisiae genome contains three genes encoding alkali metal cation/H+ antiporters (Nha1p, Nhx1p, Kha1p) that differ in cell localization, substrate specificity and physiological function. Systematic genome sequencing of other yeast species revealed highly conserved homologous ORFs in all of them. We compared the yeast sequences both at DNA and protein levels. The subfamily of yeast endosomal/prevacuolar Nhx1 antiporters is closely related to mammalian plasma membrane NHE proteins and to both plasma membrane and vacuolar plant antiporters. The high sequence conservation within this subfamily of yeast antiporters suggests that Nhx1p is of great importance in cell physiology. Yeast Kha1 proteins probably belong to the same subfamily as bacterial antiporters, whereas Nhal proteins form a distinct subfamily.

• MeSH
• DNA, Fungal analysis   MeSH
• Potassium-Hydrogen Antiporters chemistry   classification   genetics   MeSH
• Phylogeny MeSH
• Membrane Proteins chemistry   classification   genetics   MeSH
• Molecular Sequence Data MeSH
• Sodium-Hydrogen Exchangers chemistry   classification   genetics   MeSH
• Cation Transport Proteins chemistry   classification   genetics   MeSH
• Saccharomyces cerevisiae Proteins chemistry   classification   genetics   MeSH
• Amino Acid Sequence MeSH
• Sequence Analysis, DNA MeSH
• Sequence Homology, Amino Acid MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA, Fungal MeSH
• Potassium-Hydrogen Antiporters MeSH
• KHA1 protein, S cerevisiae MeSH Browser
• Membrane Proteins MeSH
• Sodium-Hydrogen Exchangers MeSH
• NHA1 protein, S cerevisiae MeSH Browser
• NHX1 protein, S cerevisiae MeSH Browser
• Cation Transport Proteins MeSH
• Saccharomyces cerevisiae Proteins MeSH

An amiloride-resistant mutant with diminished Na+/H+ antiporter activity was isolated from Methanothermobacter thermoautotrophicus. To define the protein basis of amiloride resistance, the composition of membrane-associated proteins was partially characterized and compared with that of the wild type strain. An abundant 670-kDa membrane-associated protein that was present only in the mutant strain was analyzed by MALDI-TOF MS and identified as a coenzyme F420-reducing hydrogenase. The amiloride resistance was not accompanied by changes in protein size or changes in the level of subunits A or B of the A1A0-type ATP synthase; on the other hand, the SDS-PAGE patterns of the chloroform-methanol extract of membranes from both strains were different. Two bands with calculated molecular mass 16 and 11 kDa were identified as MtrD and AtpK, respectively. The observed over-expression of a 22.7-kDa protein in the mutant cells may represent the multimeric form of the MtrD subunit. These results show that the impairment of the Na+/H+ antiporter system in the amiloride-resistant mutant of Methanothermobacter thermoautotrophicus is accompanied by only small changes in a few membrane-associated proteins.

• MeSH
• Amiloride pharmacology   MeSH
• Drug Resistance, Bacterial drug effects   genetics   physiology   MeSH
• Bacterial Proteins chemistry   drug effects   MeSH
• Sodium Channel Blockers pharmacology   MeSH
• Electrophoresis, Polyacrylamide Gel MeSH
• Membrane Proteins chemistry   drug effects   genetics   MeSH
• Methanobacteriaceae drug effects   genetics   physiology   MeSH
• Mutant Proteins chemistry   drug effects   MeSH
• Sodium-Hydrogen Exchangers chemistry   drug effects   MeSH
• Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization methods   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Amiloride MeSH
• Bacterial Proteins MeSH
• Sodium Channel Blockers MeSH
• Membrane Proteins MeSH
• Mutant Proteins MeSH
• Sodium-Hydrogen Exchangers MeSH