Vibrio cholerae has adapted to a wide range of salinity, pH and osmotic conditions, enabling it to survive passage through the host and persist in the environment. Among the many proteins responsible for bacterial survival under these diverse conditions, we have identified Vc-NhaP1 as a K(+)(Na(+))/H(+) antiporter essential for V. cholerae growth at low environmental pH. Deletion of the V. chol...

The Arabidopsis gene AtNHX1 encodes a vacuolar membrane-bound sodium/proton (Na(+)/H(+)) antiporter that transports Na(+) into the vacuole and exports H(+) into the cytoplasm. The Arabidopsis gene SOS1 encodes a plasma membrane-bound Na(+)/H(+) antiporter that exports Na(+) to the extracellular space and imports H(+) into the plant cell. Plants rely on these enzymes either to keep Na(+) out of ...

Tobacco plants were transformed with a Nhap type Na /H antiporter gene, SynnhaP1 (slr1595), from a cyanobacterium Synechocystis sp. PCC 6803. Two kinds of promoters, Arabidopsis alcohol dehydrogenase gene promoter (Adh promoter) and CaMV 35S promoter (35S promoter), were used. The transgenic plants driven by Adh promoter accumulated SynNhaP1 proteins only in root whereas the transgenic plants d...

The mechanism of mammalian polyamine transport is poorly understood. We have investigated the role of plasma-membrane potential (DeltaPsipm) in putrescine and spermidine uptake in ZR-75-1 human breast cancer cells. The rate of [3H]putrescine and [3H]spermidine uptake was inversely correlated to extracellular [K+] ([K+]o) and to DeltaPsipm, as determined by the accumulation of [3H]tetraphenylpho...

It has previously been shown (Baroin, A., F. Garcia-Romeu, T. Lamarre, and R. Motais. 1984a, b. Journal of Physiology. 350:137, 356:21; Mahé, Y., F. Garcia-Romeu, and R. Motais. 1985. European Journal of Pharmacology. 116:199) that the addition of catecholamines to an isotonic suspension of nucleated red blood cells of the rainbow trout first stimulates a cAMP-dependent, amiloride-sensitive Na+...

The Vc-NhaD is an Na + /H + antiporter from Vibrio cholerae belonging to a new family of bacterial Na + /H + antiporters, the NhaD family. In the present work we mutagenized five conserved Asp and Glu residues and one conserved Thr residue to Ala in order to identify amino acids that are critical for the antiport activity. All mutations fall into two distinct groups: (i) four variants, GluAla, ...

The effect of microenvironmental factors on the regulation of intracellular pH (pHi) in MGH U1 cells and EMT-6 cells was studied using the fluorescent pH probe 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein. Na+/H+ exchange and Na(+)-dependent Cl-/HCO3- exchange were found to be present in both cell types. The activity of both exchangers was dependent on pHi, with low levels of activit...

The human, leukemic cell line, HL-60, undergoes differentiation in response to tumor-promoting phorbol esters. Recent studies have implicated stimulation of a Na+/H+ antiporter as an initial event in cellular differentiation and/or proliferation. The effects of phorbol esters on Na+-dependent H+ efflux from HL-60 cells were studied by pH-stat titration. Tumor-promoting phorbol diesters, but not...

The present study was designed to examine the kinetics of Na(+)-H+ exchange in red blood cells of normotensive and hypertensive subjects and its relation to the previously reported abnormalities in Na(+)-Li+ exchange. The Na(+)-H+ antiporter activation kinetics were studied by varying cell pH and measuring net Na+ influx (mmol/l cell x hr = units) driven by an outward H+ gradient. The Na(+)-Li+...

The Saccharomyces cerevisiae Nha1p, a plasma membrane protein belonging to the monovalent cation/proton antiporter family, plays a key role in the salt tolerance and pH regulation of cells. We examined the molecular function of Nha1p by using secretory vesicles isolated from a temperature sensitive secretory mutant, sec4-2, in vitro. The isolated secretory vesicles contained newly synthesized N...