pH and Na+ homeostasis in all cells requires Na+/H+ antiporters. The crystal structure, obtained at pH 4, of NhaA, the main antiporter of Escherichia coli, has provided general insights into an antiporter mechanism and its unique pH regulation. Here, we describe a general method to select various NhaA mutants from a library of randomly mutagenized NhaA. The selected mutants, A167P and F267C are...

When under salt stress, plants maintain a high concentration of K(+) and a low concentration of Na(+) in the cytosol. They do this by regulating the expression and activity of K(+) and Na(+) transporters and of H(+) pumps that generate the driving force for transport. Although salt-stress sensors remain elusive, some of the intermediary signaling components have been identified. Evidence sugges...

Application of protoplast transformation and single- and double-crossover mutagenesis protocols to alkaliphilic Bacillus firmus OF4811M (an auxotrophic strain of B. firmus OF4) facilitated the extension of the sequence of the previously cloned nhaC gene, which encodes an Na+/H+ antiporter, and the surrounding region. The nhaC gene is part of a likely 2-gene operon encompassing nhaC and a small ...

In extreme alkaliphiles, Na(+)/H(+) antiporters play a central role in the Na(+) cycle that supports pH homeostasis, Na(+) resistance, solute uptake, and motility. Properties of individual antiporters have only been examined in extremely alkaliphilic soil Bacillus spp., whereas the most alkaline natural habitats usually couple high pH with high salinity. Here, studies were conducted on a Na(+)(...

The trout red blood cell Na+/H+ antiporter (beta NHE) plays two interesting properties: it is the only NHE own to be activated by cyclic AMP, and the activation process is followed by a desensitisation of the transport system itself. Cloning and expression of beta NHE have provided inificant information about Na+/H+ activation, in particular that activation by cyclic AMP is directly dependent u...

Mechanisms involved in basolateral H/OH/HCO3 transport in the in vitro microperfused rat cortical thick ascending limb were examined by the microfluorometric determination of cell pH using (2',7')-bis-(carboxyethyl)-(5,6)-carboxyfluorescein. The mean cell pH in this segment perfused with 147 mM sodium and 25 mM HCO3 at pH 7.4 was 7.13±0.02 (n = 30). Lowering bath HCO3 from 25 to 5 mM (constant ...

Mungbean is an important pulse crop extensively cultivated in Southeast Asia for supply of easily digestible protein. Salinity severely limits the growth and productivity of mungbean, and weeding poses nutritional and disease constraints to mungbean cultivation. To pyramid both salt tolerance and protection against herbicide in mungbean, the AtNHX1 encoding tonoplast Na+/H+ antiporter from Arab...